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4672 lines
171 KiB
Text
Git User's Manual (for version 1.5.3 or newer)
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______________________________________________
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Git is a fast distributed revision control system.
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This manual is designed to be readable by someone with basic UNIX
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command-line skills, but no previous knowledge of Git.
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<<repositories-and-branches>> and <<exploring-git-history>> explain how
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to fetch and study a project using git--read these chapters to learn how
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to build and test a particular version of a software project, search for
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regressions, and so on.
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People needing to do actual development will also want to read
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<<Developing-With-git>> and <<sharing-development>>.
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Further chapters cover more specialized topics.
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Comprehensive reference documentation is available through the man
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pages, or linkgit:git-help[1] command. For example, for the command
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`git clone <repo>`, you can either use:
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------------------------------------------------
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$ man git-clone
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------------------------------------------------
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or:
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------------------------------------------------
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$ git help clone
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------------------------------------------------
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With the latter, you can use the manual viewer of your choice; see
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linkgit:git-help[1] for more information.
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See also <<git-quick-start>> for a brief overview of Git commands,
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without any explanation.
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Finally, see <<todo>> for ways that you can help make this manual more
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complete.
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[[repositories-and-branches]]
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Repositories and Branches
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=========================
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[[how-to-get-a-git-repository]]
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How to get a Git repository
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---------------------------
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It will be useful to have a Git repository to experiment with as you
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read this manual.
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The best way to get one is by using the linkgit:git-clone[1] command to
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download a copy of an existing repository. If you don't already have a
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project in mind, here are some interesting examples:
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------------------------------------------------
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# Git itself (approx. 10MB download):
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$ git clone git://git.kernel.org/pub/scm/git/git.git
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# the Linux kernel (approx. 150MB download):
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$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
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------------------------------------------------
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The initial clone may be time-consuming for a large project, but you
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will only need to clone once.
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The clone command creates a new directory named after the project (`git`
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or `linux-2.6` in the examples above). After you cd into this
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directory, you will see that it contains a copy of the project files,
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called the <<def_working_tree,working tree>>, together with a special
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top-level directory named `.git`, which contains all the information
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about the history of the project.
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[[how-to-check-out]]
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How to check out a different version of a project
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-------------------------------------------------
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Git is best thought of as a tool for storing the history of a collection
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of files. It stores the history as a compressed collection of
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interrelated snapshots of the project's contents. In Git each such
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version is called a <<def_commit,commit>>.
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Those snapshots aren't necessarily all arranged in a single line from
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oldest to newest; instead, work may simultaneously proceed along
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parallel lines of development, called <<def_branch,branches>>, which may
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merge and diverge.
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A single Git repository can track development on multiple branches. It
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does this by keeping a list of <<def_head,heads>> which reference the
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latest commit on each branch; the linkgit:git-branch[1] command shows
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you the list of branch heads:
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------------------------------------------------
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$ git branch
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* master
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------------------------------------------------
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A freshly cloned repository contains a single branch head, by default
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named "master", with the working directory initialized to the state of
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the project referred to by that branch head.
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Most projects also use <<def_tag,tags>>. Tags, like heads, are
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references into the project's history, and can be listed using the
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linkgit:git-tag[1] command:
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------------------------------------------------
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$ git tag -l
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v2.6.11
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v2.6.11-tree
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v2.6.12
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v2.6.12-rc2
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v2.6.12-rc3
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v2.6.12-rc4
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v2.6.12-rc5
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v2.6.12-rc6
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v2.6.13
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...
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------------------------------------------------
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Tags are expected to always point at the same version of a project,
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while heads are expected to advance as development progresses.
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Create a new branch head pointing to one of these versions and check it
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out using linkgit:git-checkout[1]:
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------------------------------------------------
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$ git checkout -b new v2.6.13
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------------------------------------------------
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The working directory then reflects the contents that the project had
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when it was tagged v2.6.13, and linkgit:git-branch[1] shows two
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branches, with an asterisk marking the currently checked-out branch:
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------------------------------------------------
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$ git branch
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master
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* new
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------------------------------------------------
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If you decide that you'd rather see version 2.6.17, you can modify
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the current branch to point at v2.6.17 instead, with
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------------------------------------------------
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$ git reset --hard v2.6.17
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------------------------------------------------
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Note that if the current branch head was your only reference to a
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particular point in history, then resetting that branch may leave you
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with no way to find the history it used to point to; so use this command
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carefully.
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[[understanding-commits]]
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Understanding History: Commits
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------------------------------
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Every change in the history of a project is represented by a commit.
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The linkgit:git-show[1] command shows the most recent commit on the
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current branch:
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------------------------------------------------
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$ git show
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commit 17cf781661e6d38f737f15f53ab552f1e95960d7
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Author: Linus Torvalds <torvalds@ppc970.osdl.org.(none)>
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Date: Tue Apr 19 14:11:06 2005 -0700
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Remove duplicate getenv(DB_ENVIRONMENT) call
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Noted by Tony Luck.
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diff --git a/init-db.c b/init-db.c
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index 65898fa..b002dc6 100644
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--- a/init-db.c
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+++ b/init-db.c
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@@ -7,7 +7,7 @@
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int main(int argc, char **argv)
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{
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- char *sha1_dir = getenv(DB_ENVIRONMENT), *path;
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+ char *sha1_dir, *path;
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int len, i;
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if (mkdir(".git", 0755) < 0) {
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------------------------------------------------
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As you can see, a commit shows who made the latest change, what they
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did, and why.
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Every commit has a 40-hexdigit id, sometimes called the "object name" or the
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"SHA-1 id", shown on the first line of the `git show` output. You can usually
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refer to a commit by a shorter name, such as a tag or a branch name, but this
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longer name can also be useful. Most importantly, it is a globally unique
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name for this commit: so if you tell somebody else the object name (for
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example in email), then you are guaranteed that name will refer to the same
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commit in their repository that it does in yours (assuming their repository
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has that commit at all). Since the object name is computed as a hash over the
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contents of the commit, you are guaranteed that the commit can never change
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without its name also changing.
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In fact, in <<git-concepts>> we shall see that everything stored in Git
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history, including file data and directory contents, is stored in an object
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with a name that is a hash of its contents.
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[[understanding-reachability]]
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Understanding history: commits, parents, and reachability
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Every commit (except the very first commit in a project) also has a
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parent commit which shows what happened before this commit.
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Following the chain of parents will eventually take you back to the
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beginning of the project.
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However, the commits do not form a simple list; Git allows lines of
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development to diverge and then reconverge, and the point where two
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lines of development reconverge is called a "merge". The commit
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representing a merge can therefore have more than one parent, with
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each parent representing the most recent commit on one of the lines
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of development leading to that point.
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The best way to see how this works is using the linkgit:gitk[1]
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command; running gitk now on a Git repository and looking for merge
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commits will help understand how the Git organizes history.
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In the following, we say that commit X is "reachable" from commit Y
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if commit X is an ancestor of commit Y. Equivalently, you could say
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that Y is a descendant of X, or that there is a chain of parents
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leading from commit Y to commit X.
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[[history-diagrams]]
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Understanding history: History diagrams
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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We will sometimes represent Git history using diagrams like the one
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below. Commits are shown as "o", and the links between them with
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lines drawn with - / and \. Time goes left to right:
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................................................
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o--o--o <-- Branch A
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/
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o--o--o <-- master
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\
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o--o--o <-- Branch B
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................................................
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If we need to talk about a particular commit, the character "o" may
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be replaced with another letter or number.
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[[what-is-a-branch]]
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Understanding history: What is a branch?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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When we need to be precise, we will use the word "branch" to mean a line
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of development, and "branch head" (or just "head") to mean a reference
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to the most recent commit on a branch. In the example above, the branch
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head named "A" is a pointer to one particular commit, but we refer to
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the line of three commits leading up to that point as all being part of
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"branch A".
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However, when no confusion will result, we often just use the term
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"branch" both for branches and for branch heads.
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[[manipulating-branches]]
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Manipulating branches
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---------------------
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Creating, deleting, and modifying branches is quick and easy; here's
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a summary of the commands:
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`git branch`::
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list all branches
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`git branch <branch>`::
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create a new branch named `<branch>`, referencing the same
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point in history as the current branch
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`git branch <branch> <start-point>`::
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create a new branch named `<branch>`, referencing
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`<start-point>`, which may be specified any way you like,
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including using a branch name or a tag name
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`git branch -d <branch>`::
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delete the branch `<branch>`; if the branch you are deleting
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points to a commit which is not reachable from the current
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branch, this command will fail with a warning.
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`git branch -D <branch>`::
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even if the branch points to a commit not reachable
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from the current branch, you may know that that commit
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is still reachable from some other branch or tag. In that
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case it is safe to use this command to force Git to delete
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the branch.
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`git checkout <branch>`::
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make the current branch `<branch>`, updating the working
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directory to reflect the version referenced by `<branch>`
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`git checkout -b <new> <start-point>`::
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create a new branch `<new>` referencing `<start-point>`, and
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check it out.
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The special symbol "HEAD" can always be used to refer to the current
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branch. In fact, Git uses a file named `HEAD` in the `.git` directory
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to remember which branch is current:
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------------------------------------------------
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$ cat .git/HEAD
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ref: refs/heads/master
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------------------------------------------------
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[[detached-head]]
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Examining an old version without creating a new branch
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------------------------------------------------------
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The `git checkout` command normally expects a branch head, but will also
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accept an arbitrary commit; for example, you can check out the commit
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referenced by a tag:
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------------------------------------------------
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$ git checkout v2.6.17
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Note: moving to "v2.6.17" which isn't a local branch
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If you want to create a new branch from this checkout, you may do so
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(now or later) by using -b with the checkout command again. Example:
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git checkout -b <new_branch_name>
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HEAD is now at 427abfa... Linux v2.6.17
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------------------------------------------------
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The HEAD then refers to the SHA-1 of the commit instead of to a branch,
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and git branch shows that you are no longer on a branch:
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------------------------------------------------
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$ cat .git/HEAD
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427abfa28afedffadfca9dd8b067eb6d36bac53f
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$ git branch
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* (no branch)
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master
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------------------------------------------------
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In this case we say that the HEAD is "detached".
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This is an easy way to check out a particular version without having to
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make up a name for the new branch. You can still create a new branch
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(or tag) for this version later if you decide to.
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[[examining-remote-branches]]
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Examining branches from a remote repository
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-------------------------------------------
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The "master" branch that was created at the time you cloned is a copy
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of the HEAD in the repository that you cloned from. That repository
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may also have had other branches, though, and your local repository
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keeps branches which track each of those remote branches, called
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remote-tracking branches, which you
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can view using the `-r` option to linkgit:git-branch[1]:
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------------------------------------------------
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$ git branch -r
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origin/HEAD
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origin/html
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origin/maint
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origin/man
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origin/master
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origin/next
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origin/pu
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origin/todo
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------------------------------------------------
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In this example, "origin" is called a remote repository, or "remote"
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for short. The branches of this repository are called "remote
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branches" from our point of view. The remote-tracking branches listed
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above were created based on the remote branches at clone time and will
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be updated by `git fetch` (hence `git pull`) and `git push`. See
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<<Updating-a-repository-With-git-fetch>> for details.
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You might want to build on one of these remote-tracking branches
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on a branch of your own, just as you would for a tag:
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------------------------------------------------
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$ git checkout -b my-todo-copy origin/todo
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------------------------------------------------
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You can also check out `origin/todo` directly to examine it or
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write a one-off patch. See <<detached-head,detached head>>.
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Note that the name "origin" is just the name that Git uses by default
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to refer to the repository that you cloned from.
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[[how-git-stores-references]]
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Naming branches, tags, and other references
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-------------------------------------------
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Branches, remote-tracking branches, and tags are all references to
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commits. All references are named with a slash-separated path name
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starting with `refs`; the names we've been using so far are actually
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shorthand:
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- The branch `test` is short for `refs/heads/test`.
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- The tag `v2.6.18` is short for `refs/tags/v2.6.18`.
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- `origin/master` is short for `refs/remotes/origin/master`.
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The full name is occasionally useful if, for example, there ever
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exists a tag and a branch with the same name.
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(Newly created refs are actually stored in the `.git/refs` directory,
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under the path given by their name. However, for efficiency reasons
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they may also be packed together in a single file; see
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linkgit:git-pack-refs[1]).
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As another useful shortcut, the "HEAD" of a repository can be referred
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to just using the name of that repository. So, for example, "origin"
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is usually a shortcut for the HEAD branch in the repository "origin".
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For the complete list of paths which Git checks for references, and
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the order it uses to decide which to choose when there are multiple
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references with the same shorthand name, see the "SPECIFYING
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REVISIONS" section of linkgit:gitrevisions[7].
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[[Updating-a-repository-With-git-fetch]]
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Updating a repository with git fetch
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------------------------------------
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Eventually the developer cloned from will do additional work in her
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repository, creating new commits and advancing the branches to point
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at the new commits.
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The command `git fetch`, with no arguments, will update all of the
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remote-tracking branches to the latest version found in her
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repository. It will not touch any of your own branches--not even the
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"master" branch that was created for you on clone.
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[[fetching-branches]]
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Fetching branches from other repositories
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-----------------------------------------
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You can also track branches from repositories other than the one you
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cloned from, using linkgit:git-remote[1]:
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-------------------------------------------------
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$ git remote add linux-nfs git://linux-nfs.org/pub/nfs-2.6.git
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$ git fetch linux-nfs
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* refs/remotes/linux-nfs/master: storing branch 'master' ...
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commit: bf81b46
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-------------------------------------------------
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New remote-tracking branches will be stored under the shorthand name
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that you gave `git remote add`, in this case `linux-nfs`:
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-------------------------------------------------
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$ git branch -r
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linux-nfs/master
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origin/master
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-------------------------------------------------
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If you run `git fetch <remote>` later, the remote-tracking branches
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for the named `<remote>` will be updated.
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If you examine the file `.git/config`, you will see that Git has added
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a new stanza:
|
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|
|
-------------------------------------------------
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$ cat .git/config
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...
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[remote "linux-nfs"]
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url = git://linux-nfs.org/pub/nfs-2.6.git
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fetch = +refs/heads/*:refs/remotes/linux-nfs/*
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...
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-------------------------------------------------
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This is what causes Git to track the remote's branches; you may modify
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or delete these configuration options by editing `.git/config` with a
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text editor. (See the "CONFIGURATION FILE" section of
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linkgit:git-config[1] for details.)
|
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|
|
[[exploring-git-history]]
|
|
Exploring Git history
|
|
=====================
|
|
|
|
Git is best thought of as a tool for storing the history of a
|
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collection of files. It does this by storing compressed snapshots of
|
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the contents of a file hierarchy, together with "commits" which show
|
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the relationships between these snapshots.
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|
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Git provides extremely flexible and fast tools for exploring the
|
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history of a project.
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|
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We start with one specialized tool that is useful for finding the
|
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commit that introduced a bug into a project.
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|
|
[[using-bisect]]
|
|
How to use bisect to find a regression
|
|
--------------------------------------
|
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|
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Suppose version 2.6.18 of your project worked, but the version at
|
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"master" crashes. Sometimes the best way to find the cause of such a
|
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regression is to perform a brute-force search through the project's
|
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history to find the particular commit that caused the problem. The
|
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linkgit:git-bisect[1] command can help you do this:
|
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|
|
-------------------------------------------------
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$ git bisect start
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$ git bisect good v2.6.18
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$ git bisect bad master
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Bisecting: 3537 revisions left to test after this
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[65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6]
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-------------------------------------------------
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If you run `git branch` at this point, you'll see that Git has
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temporarily moved you in "(no branch)". HEAD is now detached from any
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branch and points directly to a commit (with commit id 65934...) that
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is reachable from "master" but not from v2.6.18. Compile and test it,
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and see whether it crashes. Assume it does crash. Then:
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|
|
-------------------------------------------------
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$ git bisect bad
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Bisecting: 1769 revisions left to test after this
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[7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings
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-------------------------------------------------
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checks out an older version. Continue like this, telling Git at each
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stage whether the version it gives you is good or bad, and notice
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that the number of revisions left to test is cut approximately in
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half each time.
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|
|
After about 13 tests (in this case), it will output the commit id of
|
|
the guilty commit. You can then examine the commit with
|
|
linkgit:git-show[1], find out who wrote it, and mail them your bug
|
|
report with the commit id. Finally, run
|
|
|
|
-------------------------------------------------
|
|
$ git bisect reset
|
|
-------------------------------------------------
|
|
|
|
to return you to the branch you were on before.
|
|
|
|
Note that the version which `git bisect` checks out for you at each
|
|
point is just a suggestion, and you're free to try a different
|
|
version if you think it would be a good idea. For example,
|
|
occasionally you may land on a commit that broke something unrelated;
|
|
run
|
|
|
|
-------------------------------------------------
|
|
$ git bisect visualize
|
|
-------------------------------------------------
|
|
|
|
which will run gitk and label the commit it chose with a marker that
|
|
says "bisect". Choose a safe-looking commit nearby, note its commit
|
|
id, and check it out with:
|
|
|
|
-------------------------------------------------
|
|
$ git reset --hard fb47ddb2db...
|
|
-------------------------------------------------
|
|
|
|
then test, run `bisect good` or `bisect bad` as appropriate, and
|
|
continue.
|
|
|
|
Instead of `git bisect visualize` and then `git reset --hard
|
|
fb47ddb2db...`, you might just want to tell Git that you want to skip
|
|
the current commit:
|
|
|
|
-------------------------------------------------
|
|
$ git bisect skip
|
|
-------------------------------------------------
|
|
|
|
In this case, though, Git may not eventually be able to tell the first
|
|
bad one between some first skipped commits and a later bad commit.
|
|
|
|
There are also ways to automate the bisecting process if you have a
|
|
test script that can tell a good from a bad commit. See
|
|
linkgit:git-bisect[1] for more information about this and other `git
|
|
bisect` features.
|
|
|
|
[[naming-commits]]
|
|
Naming commits
|
|
--------------
|
|
|
|
We have seen several ways of naming commits already:
|
|
|
|
- 40-hexdigit object name
|
|
- branch name: refers to the commit at the head of the given
|
|
branch
|
|
- tag name: refers to the commit pointed to by the given tag
|
|
(we've seen branches and tags are special cases of
|
|
<<how-git-stores-references,references>>).
|
|
- HEAD: refers to the head of the current branch
|
|
|
|
There are many more; see the "SPECIFYING REVISIONS" section of the
|
|
linkgit:gitrevisions[7] man page for the complete list of ways to
|
|
name revisions. Some examples:
|
|
|
|
-------------------------------------------------
|
|
$ git show fb47ddb2 # the first few characters of the object name
|
|
# are usually enough to specify it uniquely
|
|
$ git show HEAD^ # the parent of the HEAD commit
|
|
$ git show HEAD^^ # the grandparent
|
|
$ git show HEAD~4 # the great-great-grandparent
|
|
-------------------------------------------------
|
|
|
|
Recall that merge commits may have more than one parent; by default,
|
|
`^` and `~` follow the first parent listed in the commit, but you can
|
|
also choose:
|
|
|
|
-------------------------------------------------
|
|
$ git show HEAD^1 # show the first parent of HEAD
|
|
$ git show HEAD^2 # show the second parent of HEAD
|
|
-------------------------------------------------
|
|
|
|
In addition to HEAD, there are several other special names for
|
|
commits:
|
|
|
|
Merges (to be discussed later), as well as operations such as
|
|
`git reset`, which change the currently checked-out commit, generally
|
|
set ORIG_HEAD to the value HEAD had before the current operation.
|
|
|
|
The `git fetch` operation always stores the head of the last fetched
|
|
branch in FETCH_HEAD. For example, if you run `git fetch` without
|
|
specifying a local branch as the target of the operation
|
|
|
|
-------------------------------------------------
|
|
$ git fetch git://example.com/proj.git theirbranch
|
|
-------------------------------------------------
|
|
|
|
the fetched commits will still be available from FETCH_HEAD.
|
|
|
|
When we discuss merges we'll also see the special name MERGE_HEAD,
|
|
which refers to the other branch that we're merging in to the current
|
|
branch.
|
|
|
|
The linkgit:git-rev-parse[1] command is a low-level command that is
|
|
occasionally useful for translating some name for a commit to the object
|
|
name for that commit:
|
|
|
|
-------------------------------------------------
|
|
$ git rev-parse origin
|
|
e05db0fd4f31dde7005f075a84f96b360d05984b
|
|
-------------------------------------------------
|
|
|
|
[[creating-tags]]
|
|
Creating tags
|
|
-------------
|
|
|
|
We can also create a tag to refer to a particular commit; after
|
|
running
|
|
|
|
-------------------------------------------------
|
|
$ git tag stable-1 1b2e1d63ff
|
|
-------------------------------------------------
|
|
|
|
You can use `stable-1` to refer to the commit 1b2e1d63ff.
|
|
|
|
This creates a "lightweight" tag. If you would also like to include a
|
|
comment with the tag, and possibly sign it cryptographically, then you
|
|
should create a tag object instead; see the linkgit:git-tag[1] man page
|
|
for details.
|
|
|
|
[[browsing-revisions]]
|
|
Browsing revisions
|
|
------------------
|
|
|
|
The linkgit:git-log[1] command can show lists of commits. On its
|
|
own, it shows all commits reachable from the parent commit; but you
|
|
can also make more specific requests:
|
|
|
|
-------------------------------------------------
|
|
$ git log v2.5.. # commits since (not reachable from) v2.5
|
|
$ git log test..master # commits reachable from master but not test
|
|
$ git log master..test # ...reachable from test but not master
|
|
$ git log master...test # ...reachable from either test or master,
|
|
# but not both
|
|
$ git log --since="2 weeks ago" # commits from the last 2 weeks
|
|
$ git log Makefile # commits which modify Makefile
|
|
$ git log fs/ # ... which modify any file under fs/
|
|
$ git log -S'foo()' # commits which add or remove any file data
|
|
# matching the string 'foo()'
|
|
-------------------------------------------------
|
|
|
|
And of course you can combine all of these; the following finds
|
|
commits since v2.5 which touch the `Makefile` or any file under `fs`:
|
|
|
|
-------------------------------------------------
|
|
$ git log v2.5.. Makefile fs/
|
|
-------------------------------------------------
|
|
|
|
You can also ask git log to show patches:
|
|
|
|
-------------------------------------------------
|
|
$ git log -p
|
|
-------------------------------------------------
|
|
|
|
See the `--pretty` option in the linkgit:git-log[1] man page for more
|
|
display options.
|
|
|
|
Note that git log starts with the most recent commit and works
|
|
backwards through the parents; however, since Git history can contain
|
|
multiple independent lines of development, the particular order that
|
|
commits are listed in may be somewhat arbitrary.
|
|
|
|
[[generating-diffs]]
|
|
Generating diffs
|
|
----------------
|
|
|
|
You can generate diffs between any two versions using
|
|
linkgit:git-diff[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git diff master..test
|
|
-------------------------------------------------
|
|
|
|
That will produce the diff between the tips of the two branches. If
|
|
you'd prefer to find the diff from their common ancestor to test, you
|
|
can use three dots instead of two:
|
|
|
|
-------------------------------------------------
|
|
$ git diff master...test
|
|
-------------------------------------------------
|
|
|
|
Sometimes what you want instead is a set of patches; for this you can
|
|
use linkgit:git-format-patch[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git format-patch master..test
|
|
-------------------------------------------------
|
|
|
|
will generate a file with a patch for each commit reachable from test
|
|
but not from master.
|
|
|
|
[[viewing-old-file-versions]]
|
|
Viewing old file versions
|
|
-------------------------
|
|
|
|
You can always view an old version of a file by just checking out the
|
|
correct revision first. But sometimes it is more convenient to be
|
|
able to view an old version of a single file without checking
|
|
anything out; this command does that:
|
|
|
|
-------------------------------------------------
|
|
$ git show v2.5:fs/locks.c
|
|
-------------------------------------------------
|
|
|
|
Before the colon may be anything that names a commit, and after it
|
|
may be any path to a file tracked by Git.
|
|
|
|
[[history-examples]]
|
|
Examples
|
|
--------
|
|
|
|
[[counting-commits-on-a-branch]]
|
|
Counting the number of commits on a branch
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Suppose you want to know how many commits you've made on `mybranch`
|
|
since it diverged from `origin`:
|
|
|
|
-------------------------------------------------
|
|
$ git log --pretty=oneline origin..mybranch | wc -l
|
|
-------------------------------------------------
|
|
|
|
Alternatively, you may often see this sort of thing done with the
|
|
lower-level command linkgit:git-rev-list[1], which just lists the SHA-1's
|
|
of all the given commits:
|
|
|
|
-------------------------------------------------
|
|
$ git rev-list origin..mybranch | wc -l
|
|
-------------------------------------------------
|
|
|
|
[[checking-for-equal-branches]]
|
|
Check whether two branches point at the same history
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Suppose you want to check whether two branches point at the same point
|
|
in history.
|
|
|
|
-------------------------------------------------
|
|
$ git diff origin..master
|
|
-------------------------------------------------
|
|
|
|
will tell you whether the contents of the project are the same at the
|
|
two branches; in theory, however, it's possible that the same project
|
|
contents could have been arrived at by two different historical
|
|
routes. You could compare the object names:
|
|
|
|
-------------------------------------------------
|
|
$ git rev-list origin
|
|
e05db0fd4f31dde7005f075a84f96b360d05984b
|
|
$ git rev-list master
|
|
e05db0fd4f31dde7005f075a84f96b360d05984b
|
|
-------------------------------------------------
|
|
|
|
Or you could recall that the `...` operator selects all commits
|
|
contained reachable from either one reference or the other but not
|
|
both; so
|
|
|
|
-------------------------------------------------
|
|
$ git log origin...master
|
|
-------------------------------------------------
|
|
|
|
will return no commits when the two branches are equal.
|
|
|
|
[[finding-tagged-descendants]]
|
|
Find first tagged version including a given fix
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Suppose you know that the commit e05db0fd fixed a certain problem.
|
|
You'd like to find the earliest tagged release that contains that
|
|
fix.
|
|
|
|
Of course, there may be more than one answer--if the history branched
|
|
after commit e05db0fd, then there could be multiple "earliest" tagged
|
|
releases.
|
|
|
|
You could just visually inspect the commits since e05db0fd:
|
|
|
|
-------------------------------------------------
|
|
$ gitk e05db0fd..
|
|
-------------------------------------------------
|
|
|
|
Or you can use linkgit:git-name-rev[1], which will give the commit a
|
|
name based on any tag it finds pointing to one of the commit's
|
|
descendants:
|
|
|
|
-------------------------------------------------
|
|
$ git name-rev --tags e05db0fd
|
|
e05db0fd tags/v1.5.0-rc1^0~23
|
|
-------------------------------------------------
|
|
|
|
The linkgit:git-describe[1] command does the opposite, naming the
|
|
revision using a tag on which the given commit is based:
|
|
|
|
-------------------------------------------------
|
|
$ git describe e05db0fd
|
|
v1.5.0-rc0-260-ge05db0f
|
|
-------------------------------------------------
|
|
|
|
but that may sometimes help you guess which tags might come after the
|
|
given commit.
|
|
|
|
If you just want to verify whether a given tagged version contains a
|
|
given commit, you could use linkgit:git-merge-base[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git merge-base e05db0fd v1.5.0-rc1
|
|
e05db0fd4f31dde7005f075a84f96b360d05984b
|
|
-------------------------------------------------
|
|
|
|
The merge-base command finds a common ancestor of the given commits,
|
|
and always returns one or the other in the case where one is a
|
|
descendant of the other; so the above output shows that e05db0fd
|
|
actually is an ancestor of v1.5.0-rc1.
|
|
|
|
Alternatively, note that
|
|
|
|
-------------------------------------------------
|
|
$ git log v1.5.0-rc1..e05db0fd
|
|
-------------------------------------------------
|
|
|
|
will produce empty output if and only if v1.5.0-rc1 includes e05db0fd,
|
|
because it outputs only commits that are not reachable from v1.5.0-rc1.
|
|
|
|
As yet another alternative, the linkgit:git-show-branch[1] command lists
|
|
the commits reachable from its arguments with a display on the left-hand
|
|
side that indicates which arguments that commit is reachable from. So,
|
|
you can run something like
|
|
|
|
-------------------------------------------------
|
|
$ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2
|
|
! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
|
|
available
|
|
! [v1.5.0-rc0] GIT v1.5.0 preview
|
|
! [v1.5.0-rc1] GIT v1.5.0-rc1
|
|
! [v1.5.0-rc2] GIT v1.5.0-rc2
|
|
...
|
|
-------------------------------------------------
|
|
|
|
then search for a line that looks like
|
|
|
|
-------------------------------------------------
|
|
+ ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
|
|
available
|
|
-------------------------------------------------
|
|
|
|
Which shows that e05db0fd is reachable from itself, from v1.5.0-rc1, and
|
|
from v1.5.0-rc2, but not from v1.5.0-rc0.
|
|
|
|
[[showing-commits-unique-to-a-branch]]
|
|
Showing commits unique to a given branch
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Suppose you would like to see all the commits reachable from the branch
|
|
head named `master` but not from any other head in your repository.
|
|
|
|
We can list all the heads in this repository with
|
|
linkgit:git-show-ref[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git show-ref --heads
|
|
bf62196b5e363d73353a9dcf094c59595f3153b7 refs/heads/core-tutorial
|
|
db768d5504c1bb46f63ee9d6e1772bd047e05bf9 refs/heads/maint
|
|
a07157ac624b2524a059a3414e99f6f44bebc1e7 refs/heads/master
|
|
24dbc180ea14dc1aebe09f14c8ecf32010690627 refs/heads/tutorial-2
|
|
1e87486ae06626c2f31eaa63d26fc0fd646c8af2 refs/heads/tutorial-fixes
|
|
-------------------------------------------------
|
|
|
|
We can get just the branch-head names, and remove `master`, with
|
|
the help of the standard utilities cut and grep:
|
|
|
|
-------------------------------------------------
|
|
$ git show-ref --heads | cut -d' ' -f2 | grep -v '^refs/heads/master'
|
|
refs/heads/core-tutorial
|
|
refs/heads/maint
|
|
refs/heads/tutorial-2
|
|
refs/heads/tutorial-fixes
|
|
-------------------------------------------------
|
|
|
|
And then we can ask to see all the commits reachable from master
|
|
but not from these other heads:
|
|
|
|
-------------------------------------------------
|
|
$ gitk master --not $( git show-ref --heads | cut -d' ' -f2 |
|
|
grep -v '^refs/heads/master' )
|
|
-------------------------------------------------
|
|
|
|
Obviously, endless variations are possible; for example, to see all
|
|
commits reachable from some head but not from any tag in the repository:
|
|
|
|
-------------------------------------------------
|
|
$ gitk $( git show-ref --heads ) --not $( git show-ref --tags )
|
|
-------------------------------------------------
|
|
|
|
(See linkgit:gitrevisions[7] for explanations of commit-selecting
|
|
syntax such as `--not`.)
|
|
|
|
[[making-a-release]]
|
|
Creating a changelog and tarball for a software release
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
The linkgit:git-archive[1] command can create a tar or zip archive from
|
|
any version of a project; for example:
|
|
|
|
-------------------------------------------------
|
|
$ git archive -o latest.tar.gz --prefix=project/ HEAD
|
|
-------------------------------------------------
|
|
|
|
will use HEAD to produce a gzipped tar archive in which each filename
|
|
is preceded by `project/`. The output file format is inferred from
|
|
the output file extension if possible, see linkgit:git-archive[1] for
|
|
details.
|
|
|
|
Versions of Git older than 1.7.7 don't know about the `tar.gz` format,
|
|
you'll need to use gzip explicitly:
|
|
|
|
-------------------------------------------------
|
|
$ git archive --format=tar --prefix=project/ HEAD | gzip >latest.tar.gz
|
|
-------------------------------------------------
|
|
|
|
If you're releasing a new version of a software project, you may want
|
|
to simultaneously make a changelog to include in the release
|
|
announcement.
|
|
|
|
Linus Torvalds, for example, makes new kernel releases by tagging them,
|
|
then running:
|
|
|
|
-------------------------------------------------
|
|
$ release-script 2.6.12 2.6.13-rc6 2.6.13-rc7
|
|
-------------------------------------------------
|
|
|
|
where release-script is a shell script that looks like:
|
|
|
|
-------------------------------------------------
|
|
#!/bin/sh
|
|
stable="$1"
|
|
last="$2"
|
|
new="$3"
|
|
echo "# git tag v$new"
|
|
echo "git archive --prefix=linux-$new/ v$new | gzip -9 > ../linux-$new.tar.gz"
|
|
echo "git diff v$stable v$new | gzip -9 > ../patch-$new.gz"
|
|
echo "git log --no-merges v$new ^v$last > ../ChangeLog-$new"
|
|
echo "git shortlog --no-merges v$new ^v$last > ../ShortLog"
|
|
echo "git diff --stat --summary -M v$last v$new > ../diffstat-$new"
|
|
-------------------------------------------------
|
|
|
|
and then he just cut-and-pastes the output commands after verifying that
|
|
they look OK.
|
|
|
|
[[Finding-commits-With-given-Content]]
|
|
Finding commits referencing a file with given content
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Somebody hands you a copy of a file, and asks which commits modified a
|
|
file such that it contained the given content either before or after the
|
|
commit. You can find out with this:
|
|
|
|
-------------------------------------------------
|
|
$ git log --raw --abbrev=40 --pretty=oneline |
|
|
grep -B 1 `git hash-object filename`
|
|
-------------------------------------------------
|
|
|
|
Figuring out why this works is left as an exercise to the (advanced)
|
|
student. The linkgit:git-log[1], linkgit:git-diff-tree[1], and
|
|
linkgit:git-hash-object[1] man pages may prove helpful.
|
|
|
|
[[Developing-With-git]]
|
|
Developing with Git
|
|
===================
|
|
|
|
[[telling-git-your-name]]
|
|
Telling Git your name
|
|
---------------------
|
|
|
|
Before creating any commits, you should introduce yourself to Git.
|
|
The easiest way to do so is to use linkgit:git-config[1]:
|
|
|
|
------------------------------------------------
|
|
$ git config --global user.name 'Your Name Comes Here'
|
|
$ git config --global user.email 'you@yourdomain.example.com'
|
|
------------------------------------------------
|
|
|
|
Which will add the following to a file named `.gitconfig` in your
|
|
home directory:
|
|
|
|
------------------------------------------------
|
|
[user]
|
|
name = Your Name Comes Here
|
|
email = you@yourdomain.example.com
|
|
------------------------------------------------
|
|
|
|
See the "CONFIGURATION FILE" section of linkgit:git-config[1] for
|
|
details on the configuration file. The file is plain text, so you can
|
|
also edit it with your favorite editor.
|
|
|
|
|
|
[[creating-a-new-repository]]
|
|
Creating a new repository
|
|
-------------------------
|
|
|
|
Creating a new repository from scratch is very easy:
|
|
|
|
-------------------------------------------------
|
|
$ mkdir project
|
|
$ cd project
|
|
$ git init
|
|
-------------------------------------------------
|
|
|
|
If you have some initial content (say, a tarball):
|
|
|
|
-------------------------------------------------
|
|
$ tar xzvf project.tar.gz
|
|
$ cd project
|
|
$ git init
|
|
$ git add . # include everything below ./ in the first commit:
|
|
$ git commit
|
|
-------------------------------------------------
|
|
|
|
[[how-to-make-a-commit]]
|
|
How to make a commit
|
|
--------------------
|
|
|
|
Creating a new commit takes three steps:
|
|
|
|
1. Making some changes to the working directory using your
|
|
favorite editor.
|
|
2. Telling Git about your changes.
|
|
3. Creating the commit using the content you told Git about
|
|
in step 2.
|
|
|
|
In practice, you can interleave and repeat steps 1 and 2 as many
|
|
times as you want: in order to keep track of what you want committed
|
|
at step 3, Git maintains a snapshot of the tree's contents in a
|
|
special staging area called "the index."
|
|
|
|
At the beginning, the content of the index will be identical to
|
|
that of the HEAD. The command `git diff --cached`, which shows
|
|
the difference between the HEAD and the index, should therefore
|
|
produce no output at that point.
|
|
|
|
Modifying the index is easy:
|
|
|
|
To update the index with the new contents of a modified file, use
|
|
|
|
-------------------------------------------------
|
|
$ git add path/to/file
|
|
-------------------------------------------------
|
|
|
|
To add the contents of a new file to the index, use
|
|
|
|
-------------------------------------------------
|
|
$ git add path/to/file
|
|
-------------------------------------------------
|
|
|
|
To remove a file from the index and from the working tree,
|
|
|
|
-------------------------------------------------
|
|
$ git rm path/to/file
|
|
-------------------------------------------------
|
|
|
|
After each step you can verify that
|
|
|
|
-------------------------------------------------
|
|
$ git diff --cached
|
|
-------------------------------------------------
|
|
|
|
always shows the difference between the HEAD and the index file--this
|
|
is what you'd commit if you created the commit now--and that
|
|
|
|
-------------------------------------------------
|
|
$ git diff
|
|
-------------------------------------------------
|
|
|
|
shows the difference between the working tree and the index file.
|
|
|
|
Note that `git add` always adds just the current contents of a file
|
|
to the index; further changes to the same file will be ignored unless
|
|
you run `git add` on the file again.
|
|
|
|
When you're ready, just run
|
|
|
|
-------------------------------------------------
|
|
$ git commit
|
|
-------------------------------------------------
|
|
|
|
and Git will prompt you for a commit message and then create the new
|
|
commit. Check to make sure it looks like what you expected with
|
|
|
|
-------------------------------------------------
|
|
$ git show
|
|
-------------------------------------------------
|
|
|
|
As a special shortcut,
|
|
|
|
-------------------------------------------------
|
|
$ git commit -a
|
|
-------------------------------------------------
|
|
|
|
will update the index with any files that you've modified or removed
|
|
and create a commit, all in one step.
|
|
|
|
A number of commands are useful for keeping track of what you're
|
|
about to commit:
|
|
|
|
-------------------------------------------------
|
|
$ git diff --cached # difference between HEAD and the index; what
|
|
# would be committed if you ran "commit" now.
|
|
$ git diff # difference between the index file and your
|
|
# working directory; changes that would not
|
|
# be included if you ran "commit" now.
|
|
$ git diff HEAD # difference between HEAD and working tree; what
|
|
# would be committed if you ran "commit -a" now.
|
|
$ git status # a brief per-file summary of the above.
|
|
-------------------------------------------------
|
|
|
|
You can also use linkgit:git-gui[1] to create commits, view changes in
|
|
the index and the working tree files, and individually select diff hunks
|
|
for inclusion in the index (by right-clicking on the diff hunk and
|
|
choosing "Stage Hunk For Commit").
|
|
|
|
[[creating-good-commit-messages]]
|
|
Creating good commit messages
|
|
-----------------------------
|
|
|
|
Though not required, it's a good idea to begin the commit message
|
|
with a single short (less than 50 character) line summarizing the
|
|
change, followed by a blank line and then a more thorough
|
|
description. The text up to the first blank line in a commit
|
|
message is treated as the commit title, and that title is used
|
|
throughout Git. For example, linkgit:git-format-patch[1] turns a
|
|
commit into email, and it uses the title on the Subject line and the
|
|
rest of the commit in the body.
|
|
|
|
|
|
[[ignoring-files]]
|
|
Ignoring files
|
|
--------------
|
|
|
|
A project will often generate files that you do 'not' want to track with Git.
|
|
This typically includes files generated by a build process or temporary
|
|
backup files made by your editor. Of course, 'not' tracking files with Git
|
|
is just a matter of 'not' calling `git add` on them. But it quickly becomes
|
|
annoying to have these untracked files lying around; e.g. they make
|
|
`git add .` practically useless, and they keep showing up in the output of
|
|
`git status`.
|
|
|
|
You can tell Git to ignore certain files by creating a file called
|
|
`.gitignore` in the top level of your working directory, with contents
|
|
such as:
|
|
|
|
-------------------------------------------------
|
|
# Lines starting with '#' are considered comments.
|
|
# Ignore any file named foo.txt.
|
|
foo.txt
|
|
# Ignore (generated) html files,
|
|
*.html
|
|
# except foo.html which is maintained by hand.
|
|
!foo.html
|
|
# Ignore objects and archives.
|
|
*.[oa]
|
|
-------------------------------------------------
|
|
|
|
See linkgit:gitignore[5] for a detailed explanation of the syntax. You can
|
|
also place .gitignore files in other directories in your working tree, and they
|
|
will apply to those directories and their subdirectories. The `.gitignore`
|
|
files can be added to your repository like any other files (just run `git add
|
|
.gitignore` and `git commit`, as usual), which is convenient when the exclude
|
|
patterns (such as patterns matching build output files) would also make sense
|
|
for other users who clone your repository.
|
|
|
|
If you wish the exclude patterns to affect only certain repositories
|
|
(instead of every repository for a given project), you may instead put
|
|
them in a file in your repository named `.git/info/exclude`, or in any
|
|
file specified by the `core.excludesfile` configuration variable.
|
|
Some Git commands can also take exclude patterns directly on the
|
|
command line. See linkgit:gitignore[5] for the details.
|
|
|
|
[[how-to-merge]]
|
|
How to merge
|
|
------------
|
|
|
|
You can rejoin two diverging branches of development using
|
|
linkgit:git-merge[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git merge branchname
|
|
-------------------------------------------------
|
|
|
|
merges the development in the branch `branchname` into the current
|
|
branch.
|
|
|
|
A merge is made by combining the changes made in `branchname` and the
|
|
changes made up to the latest commit in your current branch since
|
|
their histories forked. The work tree is overwritten by the result of
|
|
the merge when this combining is done cleanly, or overwritten by a
|
|
half-merged results when this combining results in conflicts.
|
|
Therefore, if you have uncommitted changes touching the same files as
|
|
the ones impacted by the merge, Git will refuse to proceed. Most of
|
|
the time, you will want to commit your changes before you can merge,
|
|
and if you don't, then linkgit:git-stash[1] can take these changes
|
|
away while you're doing the merge, and reapply them afterwards.
|
|
|
|
If the changes are independent enough, Git will automatically complete
|
|
the merge and commit the result (or reuse an existing commit in case
|
|
of <<fast-forwards,fast-forward>>, see below). On the other hand,
|
|
if there are conflicts--for example, if the same file is
|
|
modified in two different ways in the remote branch and the local
|
|
branch--then you are warned; the output may look something like this:
|
|
|
|
-------------------------------------------------
|
|
$ git merge next
|
|
100% (4/4) done
|
|
Auto-merged file.txt
|
|
CONFLICT (content): Merge conflict in file.txt
|
|
Automatic merge failed; fix conflicts and then commit the result.
|
|
-------------------------------------------------
|
|
|
|
Conflict markers are left in the problematic files, and after
|
|
you resolve the conflicts manually, you can update the index
|
|
with the contents and run Git commit, as you normally would when
|
|
creating a new file.
|
|
|
|
If you examine the resulting commit using gitk, you will see that it
|
|
has two parents, one pointing to the top of the current branch, and
|
|
one to the top of the other branch.
|
|
|
|
[[resolving-a-merge]]
|
|
Resolving a merge
|
|
-----------------
|
|
|
|
When a merge isn't resolved automatically, Git leaves the index and
|
|
the working tree in a special state that gives you all the
|
|
information you need to help resolve the merge.
|
|
|
|
Files with conflicts are marked specially in the index, so until you
|
|
resolve the problem and update the index, linkgit:git-commit[1] will
|
|
fail:
|
|
|
|
-------------------------------------------------
|
|
$ git commit
|
|
file.txt: needs merge
|
|
-------------------------------------------------
|
|
|
|
Also, linkgit:git-status[1] will list those files as "unmerged", and the
|
|
files with conflicts will have conflict markers added, like this:
|
|
|
|
-------------------------------------------------
|
|
<<<<<<< HEAD:file.txt
|
|
Hello world
|
|
=======
|
|
Goodbye
|
|
>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt
|
|
-------------------------------------------------
|
|
|
|
All you need to do is edit the files to resolve the conflicts, and then
|
|
|
|
-------------------------------------------------
|
|
$ git add file.txt
|
|
$ git commit
|
|
-------------------------------------------------
|
|
|
|
Note that the commit message will already be filled in for you with
|
|
some information about the merge. Normally you can just use this
|
|
default message unchanged, but you may add additional commentary of
|
|
your own if desired.
|
|
|
|
The above is all you need to know to resolve a simple merge. But Git
|
|
also provides more information to help resolve conflicts:
|
|
|
|
[[conflict-resolution]]
|
|
Getting conflict-resolution help during a merge
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
All of the changes that Git was able to merge automatically are
|
|
already added to the index file, so linkgit:git-diff[1] shows only
|
|
the conflicts. It uses an unusual syntax:
|
|
|
|
-------------------------------------------------
|
|
$ git diff
|
|
diff --cc file.txt
|
|
index 802992c,2b60207..0000000
|
|
--- a/file.txt
|
|
+++ b/file.txt
|
|
@@@ -1,1 -1,1 +1,5 @@@
|
|
++<<<<<<< HEAD:file.txt
|
|
+Hello world
|
|
++=======
|
|
+ Goodbye
|
|
++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt
|
|
-------------------------------------------------
|
|
|
|
Recall that the commit which will be committed after we resolve this
|
|
conflict will have two parents instead of the usual one: one parent
|
|
will be HEAD, the tip of the current branch; the other will be the
|
|
tip of the other branch, which is stored temporarily in MERGE_HEAD.
|
|
|
|
During the merge, the index holds three versions of each file. Each of
|
|
these three "file stages" represents a different version of the file:
|
|
|
|
-------------------------------------------------
|
|
$ git show :1:file.txt # the file in a common ancestor of both branches
|
|
$ git show :2:file.txt # the version from HEAD.
|
|
$ git show :3:file.txt # the version from MERGE_HEAD.
|
|
-------------------------------------------------
|
|
|
|
When you ask linkgit:git-diff[1] to show the conflicts, it runs a
|
|
three-way diff between the conflicted merge results in the work tree with
|
|
stages 2 and 3 to show only hunks whose contents come from both sides,
|
|
mixed (in other words, when a hunk's merge results come only from stage 2,
|
|
that part is not conflicting and is not shown. Same for stage 3).
|
|
|
|
The diff above shows the differences between the working-tree version of
|
|
file.txt and the stage 2 and stage 3 versions. So instead of preceding
|
|
each line by a single `+` or `-`, it now uses two columns: the first
|
|
column is used for differences between the first parent and the working
|
|
directory copy, and the second for differences between the second parent
|
|
and the working directory copy. (See the "COMBINED DIFF FORMAT" section
|
|
of linkgit:git-diff-files[1] for a details of the format.)
|
|
|
|
After resolving the conflict in the obvious way (but before updating the
|
|
index), the diff will look like:
|
|
|
|
-------------------------------------------------
|
|
$ git diff
|
|
diff --cc file.txt
|
|
index 802992c,2b60207..0000000
|
|
--- a/file.txt
|
|
+++ b/file.txt
|
|
@@@ -1,1 -1,1 +1,1 @@@
|
|
- Hello world
|
|
-Goodbye
|
|
++Goodbye world
|
|
-------------------------------------------------
|
|
|
|
This shows that our resolved version deleted "Hello world" from the
|
|
first parent, deleted "Goodbye" from the second parent, and added
|
|
"Goodbye world", which was previously absent from both.
|
|
|
|
Some special diff options allow diffing the working directory against
|
|
any of these stages:
|
|
|
|
-------------------------------------------------
|
|
$ git diff -1 file.txt # diff against stage 1
|
|
$ git diff --base file.txt # same as the above
|
|
$ git diff -2 file.txt # diff against stage 2
|
|
$ git diff --ours file.txt # same as the above
|
|
$ git diff -3 file.txt # diff against stage 3
|
|
$ git diff --theirs file.txt # same as the above.
|
|
-------------------------------------------------
|
|
|
|
The linkgit:git-log[1] and linkgit:gitk[1] commands also provide special help
|
|
for merges:
|
|
|
|
-------------------------------------------------
|
|
$ git log --merge
|
|
$ gitk --merge
|
|
-------------------------------------------------
|
|
|
|
These will display all commits which exist only on HEAD or on
|
|
MERGE_HEAD, and which touch an unmerged file.
|
|
|
|
You may also use linkgit:git-mergetool[1], which lets you merge the
|
|
unmerged files using external tools such as Emacs or kdiff3.
|
|
|
|
Each time you resolve the conflicts in a file and update the index:
|
|
|
|
-------------------------------------------------
|
|
$ git add file.txt
|
|
-------------------------------------------------
|
|
|
|
the different stages of that file will be "collapsed", after which
|
|
`git diff` will (by default) no longer show diffs for that file.
|
|
|
|
[[undoing-a-merge]]
|
|
Undoing a merge
|
|
---------------
|
|
|
|
If you get stuck and decide to just give up and throw the whole mess
|
|
away, you can always return to the pre-merge state with
|
|
|
|
-------------------------------------------------
|
|
$ git reset --hard HEAD
|
|
-------------------------------------------------
|
|
|
|
Or, if you've already committed the merge that you want to throw away,
|
|
|
|
-------------------------------------------------
|
|
$ git reset --hard ORIG_HEAD
|
|
-------------------------------------------------
|
|
|
|
However, this last command can be dangerous in some cases--never
|
|
throw away a commit you have already committed if that commit may
|
|
itself have been merged into another branch, as doing so may confuse
|
|
further merges.
|
|
|
|
[[fast-forwards]]
|
|
Fast-forward merges
|
|
-------------------
|
|
|
|
There is one special case not mentioned above, which is treated
|
|
differently. Normally, a merge results in a merge commit, with two
|
|
parents, one pointing at each of the two lines of development that
|
|
were merged.
|
|
|
|
However, if the current branch is a descendant of the other--so every
|
|
commit present in the one is already contained in the other--then Git
|
|
just performs a "fast-forward"; the head of the current branch is moved
|
|
forward to point at the head of the merged-in branch, without any new
|
|
commits being created.
|
|
|
|
[[fixing-mistakes]]
|
|
Fixing mistakes
|
|
---------------
|
|
|
|
If you've messed up the working tree, but haven't yet committed your
|
|
mistake, you can return the entire working tree to the last committed
|
|
state with
|
|
|
|
-------------------------------------------------
|
|
$ git reset --hard HEAD
|
|
-------------------------------------------------
|
|
|
|
If you make a commit that you later wish you hadn't, there are two
|
|
fundamentally different ways to fix the problem:
|
|
|
|
1. You can create a new commit that undoes whatever was done
|
|
by the old commit. This is the correct thing if your
|
|
mistake has already been made public.
|
|
|
|
2. You can go back and modify the old commit. You should
|
|
never do this if you have already made the history public;
|
|
Git does not normally expect the "history" of a project to
|
|
change, and cannot correctly perform repeated merges from
|
|
a branch that has had its history changed.
|
|
|
|
[[reverting-a-commit]]
|
|
Fixing a mistake with a new commit
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Creating a new commit that reverts an earlier change is very easy;
|
|
just pass the linkgit:git-revert[1] command a reference to the bad
|
|
commit; for example, to revert the most recent commit:
|
|
|
|
-------------------------------------------------
|
|
$ git revert HEAD
|
|
-------------------------------------------------
|
|
|
|
This will create a new commit which undoes the change in HEAD. You
|
|
will be given a chance to edit the commit message for the new commit.
|
|
|
|
You can also revert an earlier change, for example, the next-to-last:
|
|
|
|
-------------------------------------------------
|
|
$ git revert HEAD^
|
|
-------------------------------------------------
|
|
|
|
In this case Git will attempt to undo the old change while leaving
|
|
intact any changes made since then. If more recent changes overlap
|
|
with the changes to be reverted, then you will be asked to fix
|
|
conflicts manually, just as in the case of <<resolving-a-merge,
|
|
resolving a merge>>.
|
|
|
|
[[fixing-a-mistake-by-rewriting-history]]
|
|
Fixing a mistake by rewriting history
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
If the problematic commit is the most recent commit, and you have not
|
|
yet made that commit public, then you may just
|
|
<<undoing-a-merge,destroy it using `git reset`>>.
|
|
|
|
Alternatively, you
|
|
can edit the working directory and update the index to fix your
|
|
mistake, just as if you were going to <<how-to-make-a-commit,create a
|
|
new commit>>, then run
|
|
|
|
-------------------------------------------------
|
|
$ git commit --amend
|
|
-------------------------------------------------
|
|
|
|
which will replace the old commit by a new commit incorporating your
|
|
changes, giving you a chance to edit the old commit message first.
|
|
|
|
Again, you should never do this to a commit that may already have
|
|
been merged into another branch; use linkgit:git-revert[1] instead in
|
|
that case.
|
|
|
|
It is also possible to replace commits further back in the history, but
|
|
this is an advanced topic to be left for
|
|
<<cleaning-up-history,another chapter>>.
|
|
|
|
[[checkout-of-path]]
|
|
Checking out an old version of a file
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
In the process of undoing a previous bad change, you may find it
|
|
useful to check out an older version of a particular file using
|
|
linkgit:git-checkout[1]. We've used `git checkout` before to switch
|
|
branches, but it has quite different behavior if it is given a path
|
|
name: the command
|
|
|
|
-------------------------------------------------
|
|
$ git checkout HEAD^ path/to/file
|
|
-------------------------------------------------
|
|
|
|
replaces path/to/file by the contents it had in the commit HEAD^, and
|
|
also updates the index to match. It does not change branches.
|
|
|
|
If you just want to look at an old version of the file, without
|
|
modifying the working directory, you can do that with
|
|
linkgit:git-show[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git show HEAD^:path/to/file
|
|
-------------------------------------------------
|
|
|
|
which will display the given version of the file.
|
|
|
|
[[interrupted-work]]
|
|
Temporarily setting aside work in progress
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
While you are in the middle of working on something complicated, you
|
|
find an unrelated but obvious and trivial bug. You would like to fix it
|
|
before continuing. You can use linkgit:git-stash[1] to save the current
|
|
state of your work, and after fixing the bug (or, optionally after doing
|
|
so on a different branch and then coming back), unstash the
|
|
work-in-progress changes.
|
|
|
|
------------------------------------------------
|
|
$ git stash save "work in progress for foo feature"
|
|
------------------------------------------------
|
|
|
|
This command will save your changes away to the `stash`, and
|
|
reset your working tree and the index to match the tip of your
|
|
current branch. Then you can make your fix as usual.
|
|
|
|
------------------------------------------------
|
|
... edit and test ...
|
|
$ git commit -a -m "blorpl: typofix"
|
|
------------------------------------------------
|
|
|
|
After that, you can go back to what you were working on with
|
|
`git stash pop`:
|
|
|
|
------------------------------------------------
|
|
$ git stash pop
|
|
------------------------------------------------
|
|
|
|
|
|
[[ensuring-good-performance]]
|
|
Ensuring good performance
|
|
-------------------------
|
|
|
|
On large repositories, Git depends on compression to keep the history
|
|
information from taking up too much space on disk or in memory. Some
|
|
Git commands may automatically run linkgit:git-gc[1], so you don't
|
|
have to worry about running it manually. However, compressing a large
|
|
repository may take a while, so you may want to call `gc` explicitly
|
|
to avoid automatic compression kicking in when it is not convenient.
|
|
|
|
|
|
[[ensuring-reliability]]
|
|
Ensuring reliability
|
|
--------------------
|
|
|
|
[[checking-for-corruption]]
|
|
Checking the repository for corruption
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
The linkgit:git-fsck[1] command runs a number of self-consistency checks
|
|
on the repository, and reports on any problems. This may take some
|
|
time.
|
|
|
|
-------------------------------------------------
|
|
$ git fsck
|
|
dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
|
|
dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
|
|
dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
|
|
dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb
|
|
dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f
|
|
dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e
|
|
dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085
|
|
dangling tree b24c2473f1fd3d91352a624795be026d64c8841f
|
|
...
|
|
-------------------------------------------------
|
|
|
|
You will see informational messages on dangling objects. They are objects
|
|
that still exist in the repository but are no longer referenced by any of
|
|
your branches, and can (and will) be removed after a while with `gc`.
|
|
You can run `git fsck --no-dangling` to suppress these messages, and still
|
|
view real errors.
|
|
|
|
[[recovering-lost-changes]]
|
|
Recovering lost changes
|
|
~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
[[reflogs]]
|
|
Reflogs
|
|
^^^^^^^
|
|
|
|
Say you modify a branch with <<fixing-mistakes,`git reset --hard`>>,
|
|
and then realize that the branch was the only reference you had to
|
|
that point in history.
|
|
|
|
Fortunately, Git also keeps a log, called a "reflog", of all the
|
|
previous values of each branch. So in this case you can still find the
|
|
old history using, for example,
|
|
|
|
-------------------------------------------------
|
|
$ git log master@{1}
|
|
-------------------------------------------------
|
|
|
|
This lists the commits reachable from the previous version of the
|
|
`master` branch head. This syntax can be used with any Git command
|
|
that accepts a commit, not just with `git log`. Some other examples:
|
|
|
|
-------------------------------------------------
|
|
$ git show master@{2} # See where the branch pointed 2,
|
|
$ git show master@{3} # 3, ... changes ago.
|
|
$ gitk master@{yesterday} # See where it pointed yesterday,
|
|
$ gitk master@{"1 week ago"} # ... or last week
|
|
$ git log --walk-reflogs master # show reflog entries for master
|
|
-------------------------------------------------
|
|
|
|
A separate reflog is kept for the HEAD, so
|
|
|
|
-------------------------------------------------
|
|
$ git show HEAD@{"1 week ago"}
|
|
-------------------------------------------------
|
|
|
|
will show what HEAD pointed to one week ago, not what the current branch
|
|
pointed to one week ago. This allows you to see the history of what
|
|
you've checked out.
|
|
|
|
The reflogs are kept by default for 30 days, after which they may be
|
|
pruned. See linkgit:git-reflog[1] and linkgit:git-gc[1] to learn
|
|
how to control this pruning, and see the "SPECIFYING REVISIONS"
|
|
section of linkgit:gitrevisions[7] for details.
|
|
|
|
Note that the reflog history is very different from normal Git history.
|
|
While normal history is shared by every repository that works on the
|
|
same project, the reflog history is not shared: it tells you only about
|
|
how the branches in your local repository have changed over time.
|
|
|
|
[[dangling-object-recovery]]
|
|
Examining dangling objects
|
|
^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
In some situations the reflog may not be able to save you. For example,
|
|
suppose you delete a branch, then realize you need the history it
|
|
contained. The reflog is also deleted; however, if you have not yet
|
|
pruned the repository, then you may still be able to find the lost
|
|
commits in the dangling objects that `git fsck` reports. See
|
|
<<dangling-objects>> for the details.
|
|
|
|
-------------------------------------------------
|
|
$ git fsck
|
|
dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
|
|
dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
|
|
dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
|
|
...
|
|
-------------------------------------------------
|
|
|
|
You can examine
|
|
one of those dangling commits with, for example,
|
|
|
|
------------------------------------------------
|
|
$ gitk 7281251ddd --not --all
|
|
------------------------------------------------
|
|
|
|
which does what it sounds like: it says that you want to see the commit
|
|
history that is described by the dangling commit(s), but not the
|
|
history that is described by all your existing branches and tags. Thus
|
|
you get exactly the history reachable from that commit that is lost.
|
|
(And notice that it might not be just one commit: we only report the
|
|
"tip of the line" as being dangling, but there might be a whole deep
|
|
and complex commit history that was dropped.)
|
|
|
|
If you decide you want the history back, you can always create a new
|
|
reference pointing to it, for example, a new branch:
|
|
|
|
------------------------------------------------
|
|
$ git branch recovered-branch 7281251ddd
|
|
------------------------------------------------
|
|
|
|
Other types of dangling objects (blobs and trees) are also possible, and
|
|
dangling objects can arise in other situations.
|
|
|
|
|
|
[[sharing-development]]
|
|
Sharing development with others
|
|
===============================
|
|
|
|
[[getting-updates-With-git-pull]]
|
|
Getting updates with git pull
|
|
-----------------------------
|
|
|
|
After you clone a repository and commit a few changes of your own, you
|
|
may wish to check the original repository for updates and merge them
|
|
into your own work.
|
|
|
|
We have already seen <<Updating-a-repository-With-git-fetch,how to
|
|
keep remote-tracking branches up to date>> with linkgit:git-fetch[1],
|
|
and how to merge two branches. So you can merge in changes from the
|
|
original repository's master branch with:
|
|
|
|
-------------------------------------------------
|
|
$ git fetch
|
|
$ git merge origin/master
|
|
-------------------------------------------------
|
|
|
|
However, the linkgit:git-pull[1] command provides a way to do this in
|
|
one step:
|
|
|
|
-------------------------------------------------
|
|
$ git pull origin master
|
|
-------------------------------------------------
|
|
|
|
In fact, if you have `master` checked out, then this branch has been
|
|
configured by `git clone` to get changes from the HEAD branch of the
|
|
origin repository. So often you can
|
|
accomplish the above with just a simple
|
|
|
|
-------------------------------------------------
|
|
$ git pull
|
|
-------------------------------------------------
|
|
|
|
This command will fetch changes from the remote branches to your
|
|
remote-tracking branches `origin/*`, and merge the default branch into
|
|
the current branch.
|
|
|
|
More generally, a branch that is created from a remote-tracking branch
|
|
will pull
|
|
by default from that branch. See the descriptions of the
|
|
`branch.<name>.remote` and `branch.<name>.merge` options in
|
|
linkgit:git-config[1], and the discussion of the `--track` option in
|
|
linkgit:git-checkout[1], to learn how to control these defaults.
|
|
|
|
In addition to saving you keystrokes, `git pull` also helps you by
|
|
producing a default commit message documenting the branch and
|
|
repository that you pulled from.
|
|
|
|
(But note that no such commit will be created in the case of a
|
|
<<fast-forwards,fast-forward>>; instead, your branch will just be
|
|
updated to point to the latest commit from the upstream branch.)
|
|
|
|
The `git pull` command can also be given `.` as the "remote" repository,
|
|
in which case it just merges in a branch from the current repository; so
|
|
the commands
|
|
|
|
-------------------------------------------------
|
|
$ git pull . branch
|
|
$ git merge branch
|
|
-------------------------------------------------
|
|
|
|
are roughly equivalent. The former is actually very commonly used.
|
|
|
|
[[submitting-patches]]
|
|
Submitting patches to a project
|
|
-------------------------------
|
|
|
|
If you just have a few changes, the simplest way to submit them may
|
|
just be to send them as patches in email:
|
|
|
|
First, use linkgit:git-format-patch[1]; for example:
|
|
|
|
-------------------------------------------------
|
|
$ git format-patch origin
|
|
-------------------------------------------------
|
|
|
|
will produce a numbered series of files in the current directory, one
|
|
for each patch in the current branch but not in `origin/HEAD`.
|
|
|
|
`git format-patch` can include an initial "cover letter". You can insert
|
|
commentary on individual patches after the three dash line which
|
|
`format-patch` places after the commit message but before the patch
|
|
itself. If you use `git notes` to track your cover letter material,
|
|
`git format-patch --notes` will include the commit's notes in a similar
|
|
manner.
|
|
|
|
You can then import these into your mail client and send them by
|
|
hand. However, if you have a lot to send at once, you may prefer to
|
|
use the linkgit:git-send-email[1] script to automate the process.
|
|
Consult the mailing list for your project first to determine how they
|
|
prefer such patches be handled.
|
|
|
|
[[importing-patches]]
|
|
Importing patches to a project
|
|
------------------------------
|
|
|
|
Git also provides a tool called linkgit:git-am[1] (am stands for
|
|
"apply mailbox"), for importing such an emailed series of patches.
|
|
Just save all of the patch-containing messages, in order, into a
|
|
single mailbox file, say `patches.mbox`, then run
|
|
|
|
-------------------------------------------------
|
|
$ git am -3 patches.mbox
|
|
-------------------------------------------------
|
|
|
|
Git will apply each patch in order; if any conflicts are found, it
|
|
will stop, and you can fix the conflicts as described in
|
|
"<<resolving-a-merge,Resolving a merge>>". (The `-3` option tells
|
|
Git to perform a merge; if you would prefer it just to abort and
|
|
leave your tree and index untouched, you may omit that option.)
|
|
|
|
Once the index is updated with the results of the conflict
|
|
resolution, instead of creating a new commit, just run
|
|
|
|
-------------------------------------------------
|
|
$ git am --resolved
|
|
-------------------------------------------------
|
|
|
|
and Git will create the commit for you and continue applying the
|
|
remaining patches from the mailbox.
|
|
|
|
The final result will be a series of commits, one for each patch in
|
|
the original mailbox, with authorship and commit log message each
|
|
taken from the message containing each patch.
|
|
|
|
[[public-repositories]]
|
|
Public Git repositories
|
|
-----------------------
|
|
|
|
Another way to submit changes to a project is to tell the maintainer
|
|
of that project to pull the changes from your repository using
|
|
linkgit:git-pull[1]. In the section "<<getting-updates-With-git-pull,
|
|
Getting updates with `git pull`>>" we described this as a way to get
|
|
updates from the "main" repository, but it works just as well in the
|
|
other direction.
|
|
|
|
If you and the maintainer both have accounts on the same machine, then
|
|
you can just pull changes from each other's repositories directly;
|
|
commands that accept repository URLs as arguments will also accept a
|
|
local directory name:
|
|
|
|
-------------------------------------------------
|
|
$ git clone /path/to/repository
|
|
$ git pull /path/to/other/repository
|
|
-------------------------------------------------
|
|
|
|
or an ssh URL:
|
|
|
|
-------------------------------------------------
|
|
$ git clone ssh://yourhost/~you/repository
|
|
-------------------------------------------------
|
|
|
|
For projects with few developers, or for synchronizing a few private
|
|
repositories, this may be all you need.
|
|
|
|
However, the more common way to do this is to maintain a separate public
|
|
repository (usually on a different host) for others to pull changes
|
|
from. This is usually more convenient, and allows you to cleanly
|
|
separate private work in progress from publicly visible work.
|
|
|
|
You will continue to do your day-to-day work in your personal
|
|
repository, but periodically "push" changes from your personal
|
|
repository into your public repository, allowing other developers to
|
|
pull from that repository. So the flow of changes, in a situation
|
|
where there is one other developer with a public repository, looks
|
|
like this:
|
|
|
|
you push
|
|
your personal repo ------------------> your public repo
|
|
^ |
|
|
| |
|
|
| you pull | they pull
|
|
| |
|
|
| |
|
|
| they push V
|
|
their public repo <------------------- their repo
|
|
|
|
We explain how to do this in the following sections.
|
|
|
|
[[setting-up-a-public-repository]]
|
|
Setting up a public repository
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Assume your personal repository is in the directory `~/proj`. We
|
|
first create a new clone of the repository and tell `git daemon` that it
|
|
is meant to be public:
|
|
|
|
-------------------------------------------------
|
|
$ git clone --bare ~/proj proj.git
|
|
$ touch proj.git/git-daemon-export-ok
|
|
-------------------------------------------------
|
|
|
|
The resulting directory proj.git contains a "bare" git repository--it is
|
|
just the contents of the `.git` directory, without any files checked out
|
|
around it.
|
|
|
|
Next, copy `proj.git` to the server where you plan to host the
|
|
public repository. You can use scp, rsync, or whatever is most
|
|
convenient.
|
|
|
|
[[exporting-via-git]]
|
|
Exporting a Git repository via the Git protocol
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
This is the preferred method.
|
|
|
|
If someone else administers the server, they should tell you what
|
|
directory to put the repository in, and what `git://` URL it will
|
|
appear at. You can then skip to the section
|
|
"<<pushing-changes-to-a-public-repository,Pushing changes to a public
|
|
repository>>", below.
|
|
|
|
Otherwise, all you need to do is start linkgit:git-daemon[1]; it will
|
|
listen on port 9418. By default, it will allow access to any directory
|
|
that looks like a Git directory and contains the magic file
|
|
git-daemon-export-ok. Passing some directory paths as `git daemon`
|
|
arguments will further restrict the exports to those paths.
|
|
|
|
You can also run `git daemon` as an inetd service; see the
|
|
linkgit:git-daemon[1] man page for details. (See especially the
|
|
examples section.)
|
|
|
|
[[exporting-via-http]]
|
|
Exporting a git repository via HTTP
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
The Git protocol gives better performance and reliability, but on a
|
|
host with a web server set up, HTTP exports may be simpler to set up.
|
|
|
|
All you need to do is place the newly created bare Git repository in
|
|
a directory that is exported by the web server, and make some
|
|
adjustments to give web clients some extra information they need:
|
|
|
|
-------------------------------------------------
|
|
$ mv proj.git /home/you/public_html/proj.git
|
|
$ cd proj.git
|
|
$ git --bare update-server-info
|
|
$ mv hooks/post-update.sample hooks/post-update
|
|
-------------------------------------------------
|
|
|
|
(For an explanation of the last two lines, see
|
|
linkgit:git-update-server-info[1] and linkgit:githooks[5].)
|
|
|
|
Advertise the URL of `proj.git`. Anybody else should then be able to
|
|
clone or pull from that URL, for example with a command line like:
|
|
|
|
-------------------------------------------------
|
|
$ git clone http://yourserver.com/~you/proj.git
|
|
-------------------------------------------------
|
|
|
|
(See also
|
|
link:howto/setup-git-server-over-http.txt[setup-git-server-over-http]
|
|
for a slightly more sophisticated setup using WebDAV which also
|
|
allows pushing over HTTP.)
|
|
|
|
[[pushing-changes-to-a-public-repository]]
|
|
Pushing changes to a public repository
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Note that the two techniques outlined above (exporting via
|
|
<<exporting-via-http,http>> or <<exporting-via-git,git>>) allow other
|
|
maintainers to fetch your latest changes, but they do not allow write
|
|
access, which you will need to update the public repository with the
|
|
latest changes created in your private repository.
|
|
|
|
The simplest way to do this is using linkgit:git-push[1] and ssh; to
|
|
update the remote branch named `master` with the latest state of your
|
|
branch named `master`, run
|
|
|
|
-------------------------------------------------
|
|
$ git push ssh://yourserver.com/~you/proj.git master:master
|
|
-------------------------------------------------
|
|
|
|
or just
|
|
|
|
-------------------------------------------------
|
|
$ git push ssh://yourserver.com/~you/proj.git master
|
|
-------------------------------------------------
|
|
|
|
As with `git fetch`, `git push` will complain if this does not result in a
|
|
<<fast-forwards,fast-forward>>; see the following section for details on
|
|
handling this case.
|
|
|
|
Note that the target of a `push` is normally a
|
|
<<def_bare_repository,bare>> repository. You can also push to a
|
|
repository that has a checked-out working tree, but a push to update the
|
|
currently checked-out branch is denied by default to prevent confusion.
|
|
See the description of the receive.denyCurrentBranch option
|
|
in linkgit:git-config[1] for details.
|
|
|
|
As with `git fetch`, you may also set up configuration options to
|
|
save typing; so, for example:
|
|
|
|
-------------------------------------------------
|
|
$ git remote add public-repo ssh://yourserver.com/~you/proj.git
|
|
-------------------------------------------------
|
|
|
|
adds the following to `.git/config`:
|
|
|
|
-------------------------------------------------
|
|
[remote "public-repo"]
|
|
url = yourserver.com:proj.git
|
|
fetch = +refs/heads/*:refs/remotes/example/*
|
|
-------------------------------------------------
|
|
|
|
which lets you do the same push with just
|
|
|
|
-------------------------------------------------
|
|
$ git push public-repo master
|
|
-------------------------------------------------
|
|
|
|
See the explanations of the `remote.<name>.url`,
|
|
`branch.<name>.remote`, and `remote.<name>.push` options in
|
|
linkgit:git-config[1] for details.
|
|
|
|
[[forcing-push]]
|
|
What to do when a push fails
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
If a push would not result in a <<fast-forwards,fast-forward>> of the
|
|
remote branch, then it will fail with an error like:
|
|
|
|
-------------------------------------------------
|
|
error: remote 'refs/heads/master' is not an ancestor of
|
|
local 'refs/heads/master'.
|
|
Maybe you are not up-to-date and need to pull first?
|
|
error: failed to push to 'ssh://yourserver.com/~you/proj.git'
|
|
-------------------------------------------------
|
|
|
|
This can happen, for example, if you:
|
|
|
|
- use `git reset --hard` to remove already-published commits, or
|
|
- use `git commit --amend` to replace already-published commits
|
|
(as in <<fixing-a-mistake-by-rewriting-history>>), or
|
|
- use `git rebase` to rebase any already-published commits (as
|
|
in <<using-git-rebase>>).
|
|
|
|
You may force `git push` to perform the update anyway by preceding the
|
|
branch name with a plus sign:
|
|
|
|
-------------------------------------------------
|
|
$ git push ssh://yourserver.com/~you/proj.git +master
|
|
-------------------------------------------------
|
|
|
|
Note the addition of the `+` sign. Alternatively, you can use the
|
|
`-f` flag to force the remote update, as in:
|
|
|
|
-------------------------------------------------
|
|
$ git push -f ssh://yourserver.com/~you/proj.git master
|
|
-------------------------------------------------
|
|
|
|
Normally whenever a branch head in a public repository is modified, it
|
|
is modified to point to a descendant of the commit that it pointed to
|
|
before. By forcing a push in this situation, you break that convention.
|
|
(See <<problems-With-rewriting-history>>.)
|
|
|
|
Nevertheless, this is a common practice for people that need a simple
|
|
way to publish a work-in-progress patch series, and it is an acceptable
|
|
compromise as long as you warn other developers that this is how you
|
|
intend to manage the branch.
|
|
|
|
It's also possible for a push to fail in this way when other people have
|
|
the right to push to the same repository. In that case, the correct
|
|
solution is to retry the push after first updating your work: either by a
|
|
pull, or by a fetch followed by a rebase; see the
|
|
<<setting-up-a-shared-repository,next section>> and
|
|
linkgit:gitcvs-migration[7] for more.
|
|
|
|
[[setting-up-a-shared-repository]]
|
|
Setting up a shared repository
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Another way to collaborate is by using a model similar to that
|
|
commonly used in CVS, where several developers with special rights
|
|
all push to and pull from a single shared repository. See
|
|
linkgit:gitcvs-migration[7] for instructions on how to
|
|
set this up.
|
|
|
|
However, while there is nothing wrong with Git's support for shared
|
|
repositories, this mode of operation is not generally recommended,
|
|
simply because the mode of collaboration that Git supports--by
|
|
exchanging patches and pulling from public repositories--has so many
|
|
advantages over the central shared repository:
|
|
|
|
- Git's ability to quickly import and merge patches allows a
|
|
single maintainer to process incoming changes even at very
|
|
high rates. And when that becomes too much, `git pull` provides
|
|
an easy way for that maintainer to delegate this job to other
|
|
maintainers while still allowing optional review of incoming
|
|
changes.
|
|
- Since every developer's repository has the same complete copy
|
|
of the project history, no repository is special, and it is
|
|
trivial for another developer to take over maintenance of a
|
|
project, either by mutual agreement, or because a maintainer
|
|
becomes unresponsive or difficult to work with.
|
|
- The lack of a central group of "committers" means there is
|
|
less need for formal decisions about who is "in" and who is
|
|
"out".
|
|
|
|
[[setting-up-gitweb]]
|
|
Allowing web browsing of a repository
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
The gitweb cgi script provides users an easy way to browse your
|
|
project's files and history without having to install Git; see the file
|
|
gitweb/INSTALL in the Git source tree for instructions on setting it up.
|
|
|
|
[[sharing-development-examples]]
|
|
Examples
|
|
--------
|
|
|
|
[[maintaining-topic-branches]]
|
|
Maintaining topic branches for a Linux subsystem maintainer
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
This describes how Tony Luck uses Git in his role as maintainer of the
|
|
IA64 architecture for the Linux kernel.
|
|
|
|
He uses two public branches:
|
|
|
|
- A "test" tree into which patches are initially placed so that they
|
|
can get some exposure when integrated with other ongoing development.
|
|
This tree is available to Andrew for pulling into -mm whenever he
|
|
wants.
|
|
|
|
- A "release" tree into which tested patches are moved for final sanity
|
|
checking, and as a vehicle to send them upstream to Linus (by sending
|
|
him a "please pull" request.)
|
|
|
|
He also uses a set of temporary branches ("topic branches"), each
|
|
containing a logical grouping of patches.
|
|
|
|
To set this up, first create your work tree by cloning Linus's public
|
|
tree:
|
|
|
|
-------------------------------------------------
|
|
$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git work
|
|
$ cd work
|
|
-------------------------------------------------
|
|
|
|
Linus's tree will be stored in the remote-tracking branch named origin/master,
|
|
and can be updated using linkgit:git-fetch[1]; you can track other
|
|
public trees using linkgit:git-remote[1] to set up a "remote" and
|
|
linkgit:git-fetch[1] to keep them up-to-date; see
|
|
<<repositories-and-branches>>.
|
|
|
|
Now create the branches in which you are going to work; these start out
|
|
at the current tip of origin/master branch, and should be set up (using
|
|
the `--track` option to linkgit:git-branch[1]) to merge changes in from
|
|
Linus by default.
|
|
|
|
-------------------------------------------------
|
|
$ git branch --track test origin/master
|
|
$ git branch --track release origin/master
|
|
-------------------------------------------------
|
|
|
|
These can be easily kept up to date using linkgit:git-pull[1].
|
|
|
|
-------------------------------------------------
|
|
$ git checkout test && git pull
|
|
$ git checkout release && git pull
|
|
-------------------------------------------------
|
|
|
|
Important note! If you have any local changes in these branches, then
|
|
this merge will create a commit object in the history (with no local
|
|
changes Git will simply do a "fast-forward" merge). Many people dislike
|
|
the "noise" that this creates in the Linux history, so you should avoid
|
|
doing this capriciously in the `release` branch, as these noisy commits
|
|
will become part of the permanent history when you ask Linus to pull
|
|
from the release branch.
|
|
|
|
A few configuration variables (see linkgit:git-config[1]) can
|
|
make it easy to push both branches to your public tree. (See
|
|
<<setting-up-a-public-repository>>.)
|
|
|
|
-------------------------------------------------
|
|
$ cat >> .git/config <<EOF
|
|
[remote "mytree"]
|
|
url = master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux-2.6.git
|
|
push = release
|
|
push = test
|
|
EOF
|
|
-------------------------------------------------
|
|
|
|
Then you can push both the test and release trees using
|
|
linkgit:git-push[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git push mytree
|
|
-------------------------------------------------
|
|
|
|
or push just one of the test and release branches using:
|
|
|
|
-------------------------------------------------
|
|
$ git push mytree test
|
|
-------------------------------------------------
|
|
|
|
or
|
|
|
|
-------------------------------------------------
|
|
$ git push mytree release
|
|
-------------------------------------------------
|
|
|
|
Now to apply some patches from the community. Think of a short
|
|
snappy name for a branch to hold this patch (or related group of
|
|
patches), and create a new branch from a recent stable tag of
|
|
Linus's branch. Picking a stable base for your branch will:
|
|
1) help you: by avoiding inclusion of unrelated and perhaps lightly
|
|
tested changes
|
|
2) help future bug hunters that use `git bisect` to find problems
|
|
|
|
-------------------------------------------------
|
|
$ git checkout -b speed-up-spinlocks v2.6.35
|
|
-------------------------------------------------
|
|
|
|
Now you apply the patch(es), run some tests, and commit the change(s). If
|
|
the patch is a multi-part series, then you should apply each as a separate
|
|
commit to this branch.
|
|
|
|
-------------------------------------------------
|
|
$ ... patch ... test ... commit [ ... patch ... test ... commit ]*
|
|
-------------------------------------------------
|
|
|
|
When you are happy with the state of this change, you can pull it into the
|
|
"test" branch in preparation to make it public:
|
|
|
|
-------------------------------------------------
|
|
$ git checkout test && git pull . speed-up-spinlocks
|
|
-------------------------------------------------
|
|
|
|
It is unlikely that you would have any conflicts here ... but you might if you
|
|
spent a while on this step and had also pulled new versions from upstream.
|
|
|
|
Some time later when enough time has passed and testing done, you can pull the
|
|
same branch into the `release` tree ready to go upstream. This is where you
|
|
see the value of keeping each patch (or patch series) in its own branch. It
|
|
means that the patches can be moved into the `release` tree in any order.
|
|
|
|
-------------------------------------------------
|
|
$ git checkout release && git pull . speed-up-spinlocks
|
|
-------------------------------------------------
|
|
|
|
After a while, you will have a number of branches, and despite the
|
|
well chosen names you picked for each of them, you may forget what
|
|
they are for, or what status they are in. To get a reminder of what
|
|
changes are in a specific branch, use:
|
|
|
|
-------------------------------------------------
|
|
$ git log linux..branchname | git shortlog
|
|
-------------------------------------------------
|
|
|
|
To see whether it has already been merged into the test or release branches,
|
|
use:
|
|
|
|
-------------------------------------------------
|
|
$ git log test..branchname
|
|
-------------------------------------------------
|
|
|
|
or
|
|
|
|
-------------------------------------------------
|
|
$ git log release..branchname
|
|
-------------------------------------------------
|
|
|
|
(If this branch has not yet been merged, you will see some log entries.
|
|
If it has been merged, then there will be no output.)
|
|
|
|
Once a patch completes the great cycle (moving from test to release,
|
|
then pulled by Linus, and finally coming back into your local
|
|
`origin/master` branch), the branch for this change is no longer needed.
|
|
You detect this when the output from:
|
|
|
|
-------------------------------------------------
|
|
$ git log origin..branchname
|
|
-------------------------------------------------
|
|
|
|
is empty. At this point the branch can be deleted:
|
|
|
|
-------------------------------------------------
|
|
$ git branch -d branchname
|
|
-------------------------------------------------
|
|
|
|
Some changes are so trivial that it is not necessary to create a separate
|
|
branch and then merge into each of the test and release branches. For
|
|
these changes, just apply directly to the `release` branch, and then
|
|
merge that into the `test` branch.
|
|
|
|
After pushing your work to `mytree`, you can use
|
|
linkgit:git-request-pull[1] to prepare a "please pull" request message
|
|
to send to Linus:
|
|
|
|
-------------------------------------------------
|
|
$ git push mytree
|
|
$ git request-pull origin mytree release
|
|
-------------------------------------------------
|
|
|
|
Here are some of the scripts that simplify all this even further.
|
|
|
|
-------------------------------------------------
|
|
==== update script ====
|
|
# Update a branch in my Git tree. If the branch to be updated
|
|
# is origin, then pull from kernel.org. Otherwise merge
|
|
# origin/master branch into test|release branch
|
|
|
|
case "$1" in
|
|
test|release)
|
|
git checkout $1 && git pull . origin
|
|
;;
|
|
origin)
|
|
before=$(git rev-parse refs/remotes/origin/master)
|
|
git fetch origin
|
|
after=$(git rev-parse refs/remotes/origin/master)
|
|
if [ $before != $after ]
|
|
then
|
|
git log $before..$after | git shortlog
|
|
fi
|
|
;;
|
|
*)
|
|
echo "usage: $0 origin|test|release" 1>&2
|
|
exit 1
|
|
;;
|
|
esac
|
|
-------------------------------------------------
|
|
|
|
-------------------------------------------------
|
|
==== merge script ====
|
|
# Merge a branch into either the test or release branch
|
|
|
|
pname=$0
|
|
|
|
usage()
|
|
{
|
|
echo "usage: $pname branch test|release" 1>&2
|
|
exit 1
|
|
}
|
|
|
|
git show-ref -q --verify -- refs/heads/"$1" || {
|
|
echo "Can't see branch <$1>" 1>&2
|
|
usage
|
|
}
|
|
|
|
case "$2" in
|
|
test|release)
|
|
if [ $(git log $2..$1 | wc -c) -eq 0 ]
|
|
then
|
|
echo $1 already merged into $2 1>&2
|
|
exit 1
|
|
fi
|
|
git checkout $2 && git pull . $1
|
|
;;
|
|
*)
|
|
usage
|
|
;;
|
|
esac
|
|
-------------------------------------------------
|
|
|
|
-------------------------------------------------
|
|
==== status script ====
|
|
# report on status of my ia64 Git tree
|
|
|
|
gb=$(tput setab 2)
|
|
rb=$(tput setab 1)
|
|
restore=$(tput setab 9)
|
|
|
|
if [ `git rev-list test..release | wc -c` -gt 0 ]
|
|
then
|
|
echo $rb Warning: commits in release that are not in test $restore
|
|
git log test..release
|
|
fi
|
|
|
|
for branch in `git show-ref --heads | sed 's|^.*/||'`
|
|
do
|
|
if [ $branch = test -o $branch = release ]
|
|
then
|
|
continue
|
|
fi
|
|
|
|
echo -n $gb ======= $branch ====== $restore " "
|
|
status=
|
|
for ref in test release origin/master
|
|
do
|
|
if [ `git rev-list $ref..$branch | wc -c` -gt 0 ]
|
|
then
|
|
status=$status${ref:0:1}
|
|
fi
|
|
done
|
|
case $status in
|
|
trl)
|
|
echo $rb Need to pull into test $restore
|
|
;;
|
|
rl)
|
|
echo "In test"
|
|
;;
|
|
l)
|
|
echo "Waiting for linus"
|
|
;;
|
|
"")
|
|
echo $rb All done $restore
|
|
;;
|
|
*)
|
|
echo $rb "<$status>" $restore
|
|
;;
|
|
esac
|
|
git log origin/master..$branch | git shortlog
|
|
done
|
|
-------------------------------------------------
|
|
|
|
|
|
[[cleaning-up-history]]
|
|
Rewriting history and maintaining patch series
|
|
==============================================
|
|
|
|
Normally commits are only added to a project, never taken away or
|
|
replaced. Git is designed with this assumption, and violating it will
|
|
cause Git's merge machinery (for example) to do the wrong thing.
|
|
|
|
However, there is a situation in which it can be useful to violate this
|
|
assumption.
|
|
|
|
[[patch-series]]
|
|
Creating the perfect patch series
|
|
---------------------------------
|
|
|
|
Suppose you are a contributor to a large project, and you want to add a
|
|
complicated feature, and to present it to the other developers in a way
|
|
that makes it easy for them to read your changes, verify that they are
|
|
correct, and understand why you made each change.
|
|
|
|
If you present all of your changes as a single patch (or commit), they
|
|
may find that it is too much to digest all at once.
|
|
|
|
If you present them with the entire history of your work, complete with
|
|
mistakes, corrections, and dead ends, they may be overwhelmed.
|
|
|
|
So the ideal is usually to produce a series of patches such that:
|
|
|
|
1. Each patch can be applied in order.
|
|
|
|
2. Each patch includes a single logical change, together with a
|
|
message explaining the change.
|
|
|
|
3. No patch introduces a regression: after applying any initial
|
|
part of the series, the resulting project still compiles and
|
|
works, and has no bugs that it didn't have before.
|
|
|
|
4. The complete series produces the same end result as your own
|
|
(probably much messier!) development process did.
|
|
|
|
We will introduce some tools that can help you do this, explain how to
|
|
use them, and then explain some of the problems that can arise because
|
|
you are rewriting history.
|
|
|
|
[[using-git-rebase]]
|
|
Keeping a patch series up to date using git rebase
|
|
--------------------------------------------------
|
|
|
|
Suppose that you create a branch `mywork` on a remote-tracking branch
|
|
`origin`, and create some commits on top of it:
|
|
|
|
-------------------------------------------------
|
|
$ git checkout -b mywork origin
|
|
$ vi file.txt
|
|
$ git commit
|
|
$ vi otherfile.txt
|
|
$ git commit
|
|
...
|
|
-------------------------------------------------
|
|
|
|
You have performed no merges into mywork, so it is just a simple linear
|
|
sequence of patches on top of `origin`:
|
|
|
|
................................................
|
|
o--o--O <-- origin
|
|
\
|
|
a--b--c <-- mywork
|
|
................................................
|
|
|
|
Some more interesting work has been done in the upstream project, and
|
|
`origin` has advanced:
|
|
|
|
................................................
|
|
o--o--O--o--o--o <-- origin
|
|
\
|
|
a--b--c <-- mywork
|
|
................................................
|
|
|
|
At this point, you could use `pull` to merge your changes back in;
|
|
the result would create a new merge commit, like this:
|
|
|
|
................................................
|
|
o--o--O--o--o--o <-- origin
|
|
\ \
|
|
a--b--c--m <-- mywork
|
|
................................................
|
|
|
|
However, if you prefer to keep the history in mywork a simple series of
|
|
commits without any merges, you may instead choose to use
|
|
linkgit:git-rebase[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git checkout mywork
|
|
$ git rebase origin
|
|
-------------------------------------------------
|
|
|
|
This will remove each of your commits from mywork, temporarily saving
|
|
them as patches (in a directory named `.git/rebase-apply`), update mywork to
|
|
point at the latest version of origin, then apply each of the saved
|
|
patches to the new mywork. The result will look like:
|
|
|
|
|
|
................................................
|
|
o--o--O--o--o--o <-- origin
|
|
\
|
|
a'--b'--c' <-- mywork
|
|
................................................
|
|
|
|
In the process, it may discover conflicts. In that case it will stop
|
|
and allow you to fix the conflicts; after fixing conflicts, use `git add`
|
|
to update the index with those contents, and then, instead of
|
|
running `git commit`, just run
|
|
|
|
-------------------------------------------------
|
|
$ git rebase --continue
|
|
-------------------------------------------------
|
|
|
|
and Git will continue applying the rest of the patches.
|
|
|
|
At any point you may use the `--abort` option to abort this process and
|
|
return mywork to the state it had before you started the rebase:
|
|
|
|
-------------------------------------------------
|
|
$ git rebase --abort
|
|
-------------------------------------------------
|
|
|
|
If you need to reorder or edit a number of commits in a branch, it may
|
|
be easier to use `git rebase -i`, which allows you to reorder and
|
|
squash commits, as well as marking them for individual editing during
|
|
the rebase. See <<interactive-rebase>> for details, and
|
|
<<reordering-patch-series>> for alternatives.
|
|
|
|
[[rewriting-one-commit]]
|
|
Rewriting a single commit
|
|
-------------------------
|
|
|
|
We saw in <<fixing-a-mistake-by-rewriting-history>> that you can replace the
|
|
most recent commit using
|
|
|
|
-------------------------------------------------
|
|
$ git commit --amend
|
|
-------------------------------------------------
|
|
|
|
which will replace the old commit by a new commit incorporating your
|
|
changes, giving you a chance to edit the old commit message first.
|
|
This is useful for fixing typos in your last commit, or for adjusting
|
|
the patch contents of a poorly staged commit.
|
|
|
|
If you need to amend commits from deeper in your history, you can
|
|
use <<interactive-rebase,interactive rebase's `edit` instruction>>.
|
|
|
|
[[reordering-patch-series]]
|
|
Reordering or selecting from a patch series
|
|
-------------------------------------------
|
|
|
|
Sometimes you want to edit a commit deeper in your history. One
|
|
approach is to use `git format-patch` to create a series of patches
|
|
and then reset the state to before the patches:
|
|
|
|
-------------------------------------------------
|
|
$ git format-patch origin
|
|
$ git reset --hard origin
|
|
-------------------------------------------------
|
|
|
|
Then modify, reorder, or eliminate patches as needed before applying
|
|
them again with linkgit:git-am[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git am *.patch
|
|
-------------------------------------------------
|
|
|
|
[[interactive-rebase]]
|
|
Using interactive rebases
|
|
-------------------------
|
|
|
|
You can also edit a patch series with an interactive rebase. This is
|
|
the same as <<reordering-patch-series,reordering a patch series using
|
|
`format-patch`>>, so use whichever interface you like best.
|
|
|
|
Rebase your current HEAD on the last commit you want to retain as-is.
|
|
For example, if you want to reorder the last 5 commits, use:
|
|
|
|
-------------------------------------------------
|
|
$ git rebase -i HEAD~5
|
|
-------------------------------------------------
|
|
|
|
This will open your editor with a list of steps to be taken to perform
|
|
your rebase.
|
|
|
|
-------------------------------------------------
|
|
pick deadbee The oneline of this commit
|
|
pick fa1afe1 The oneline of the next commit
|
|
...
|
|
|
|
# Rebase c0ffeee..deadbee onto c0ffeee
|
|
#
|
|
# Commands:
|
|
# p, pick = use commit
|
|
# r, reword = use commit, but edit the commit message
|
|
# e, edit = use commit, but stop for amending
|
|
# s, squash = use commit, but meld into previous commit
|
|
# f, fixup = like "squash", but discard this commit's log message
|
|
# x, exec = run command (the rest of the line) using shell
|
|
#
|
|
# These lines can be re-ordered; they are executed from top to bottom.
|
|
#
|
|
# If you remove a line here THAT COMMIT WILL BE LOST.
|
|
#
|
|
# However, if you remove everything, the rebase will be aborted.
|
|
#
|
|
# Note that empty commits are commented out
|
|
-------------------------------------------------
|
|
|
|
As explained in the comments, you can reorder commits, squash them
|
|
together, edit commit messages, etc. by editing the list. Once you
|
|
are satisfied, save the list and close your editor, and the rebase
|
|
will begin.
|
|
|
|
The rebase will stop where `pick` has been replaced with `edit` or
|
|
when a step in the list fails to mechanically resolve conflicts and
|
|
needs your help. When you are done editing and/or resolving conflicts
|
|
you can continue with `git rebase --continue`. If you decide that
|
|
things are getting too hairy, you can always bail out with `git rebase
|
|
--abort`. Even after the rebase is complete, you can still recover
|
|
the original branch by using the <<reflogs,reflog>>.
|
|
|
|
For a more detailed discussion of the procedure and additional tips,
|
|
see the "INTERACTIVE MODE" section of linkgit:git-rebase[1].
|
|
|
|
[[patch-series-tools]]
|
|
Other tools
|
|
-----------
|
|
|
|
There are numerous other tools, such as StGit, which exist for the
|
|
purpose of maintaining a patch series. These are outside of the scope of
|
|
this manual.
|
|
|
|
[[problems-With-rewriting-history]]
|
|
Problems with rewriting history
|
|
-------------------------------
|
|
|
|
The primary problem with rewriting the history of a branch has to do
|
|
with merging. Suppose somebody fetches your branch and merges it into
|
|
their branch, with a result something like this:
|
|
|
|
................................................
|
|
o--o--O--o--o--o <-- origin
|
|
\ \
|
|
t--t--t--m <-- their branch:
|
|
................................................
|
|
|
|
Then suppose you modify the last three commits:
|
|
|
|
................................................
|
|
o--o--o <-- new head of origin
|
|
/
|
|
o--o--O--o--o--o <-- old head of origin
|
|
................................................
|
|
|
|
If we examined all this history together in one repository, it will
|
|
look like:
|
|
|
|
................................................
|
|
o--o--o <-- new head of origin
|
|
/
|
|
o--o--O--o--o--o <-- old head of origin
|
|
\ \
|
|
t--t--t--m <-- their branch:
|
|
................................................
|
|
|
|
Git has no way of knowing that the new head is an updated version of
|
|
the old head; it treats this situation exactly the same as it would if
|
|
two developers had independently done the work on the old and new heads
|
|
in parallel. At this point, if someone attempts to merge the new head
|
|
in to their branch, Git will attempt to merge together the two (old and
|
|
new) lines of development, instead of trying to replace the old by the
|
|
new. The results are likely to be unexpected.
|
|
|
|
You may still choose to publish branches whose history is rewritten,
|
|
and it may be useful for others to be able to fetch those branches in
|
|
order to examine or test them, but they should not attempt to pull such
|
|
branches into their own work.
|
|
|
|
For true distributed development that supports proper merging,
|
|
published branches should never be rewritten.
|
|
|
|
[[bisect-merges]]
|
|
Why bisecting merge commits can be harder than bisecting linear history
|
|
-----------------------------------------------------------------------
|
|
|
|
The linkgit:git-bisect[1] command correctly handles history that
|
|
includes merge commits. However, when the commit that it finds is a
|
|
merge commit, the user may need to work harder than usual to figure out
|
|
why that commit introduced a problem.
|
|
|
|
Imagine this history:
|
|
|
|
................................................
|
|
---Z---o---X---...---o---A---C---D
|
|
\ /
|
|
o---o---Y---...---o---B
|
|
................................................
|
|
|
|
Suppose that on the upper line of development, the meaning of one
|
|
of the functions that exists at Z is changed at commit X. The
|
|
commits from Z leading to A change both the function's
|
|
implementation and all calling sites that exist at Z, as well
|
|
as new calling sites they add, to be consistent. There is no
|
|
bug at A.
|
|
|
|
Suppose that in the meantime on the lower line of development somebody
|
|
adds a new calling site for that function at commit Y. The
|
|
commits from Z leading to B all assume the old semantics of that
|
|
function and the callers and the callee are consistent with each
|
|
other. There is no bug at B, either.
|
|
|
|
Suppose further that the two development lines merge cleanly at C,
|
|
so no conflict resolution is required.
|
|
|
|
Nevertheless, the code at C is broken, because the callers added
|
|
on the lower line of development have not been converted to the new
|
|
semantics introduced on the upper line of development. So if all
|
|
you know is that D is bad, that Z is good, and that
|
|
linkgit:git-bisect[1] identifies C as the culprit, how will you
|
|
figure out that the problem is due to this change in semantics?
|
|
|
|
When the result of a `git bisect` is a non-merge commit, you should
|
|
normally be able to discover the problem by examining just that commit.
|
|
Developers can make this easy by breaking their changes into small
|
|
self-contained commits. That won't help in the case above, however,
|
|
because the problem isn't obvious from examination of any single
|
|
commit; instead, a global view of the development is required. To
|
|
make matters worse, the change in semantics in the problematic
|
|
function may be just one small part of the changes in the upper
|
|
line of development.
|
|
|
|
On the other hand, if instead of merging at C you had rebased the
|
|
history between Z to B on top of A, you would have gotten this
|
|
linear history:
|
|
|
|
................................................................
|
|
---Z---o---X--...---o---A---o---o---Y*--...---o---B*--D*
|
|
................................................................
|
|
|
|
Bisecting between Z and D* would hit a single culprit commit Y*,
|
|
and understanding why Y* was broken would probably be easier.
|
|
|
|
Partly for this reason, many experienced Git users, even when
|
|
working on an otherwise merge-heavy project, keep the history
|
|
linear by rebasing against the latest upstream version before
|
|
publishing.
|
|
|
|
[[advanced-branch-management]]
|
|
Advanced branch management
|
|
==========================
|
|
|
|
[[fetching-individual-branches]]
|
|
Fetching individual branches
|
|
----------------------------
|
|
|
|
Instead of using linkgit:git-remote[1], you can also choose just
|
|
to update one branch at a time, and to store it locally under an
|
|
arbitrary name:
|
|
|
|
-------------------------------------------------
|
|
$ git fetch origin todo:my-todo-work
|
|
-------------------------------------------------
|
|
|
|
The first argument, `origin`, just tells Git to fetch from the
|
|
repository you originally cloned from. The second argument tells Git
|
|
to fetch the branch named `todo` from the remote repository, and to
|
|
store it locally under the name `refs/heads/my-todo-work`.
|
|
|
|
You can also fetch branches from other repositories; so
|
|
|
|
-------------------------------------------------
|
|
$ git fetch git://example.com/proj.git master:example-master
|
|
-------------------------------------------------
|
|
|
|
will create a new branch named `example-master` and store in it the
|
|
branch named `master` from the repository at the given URL. If you
|
|
already have a branch named example-master, it will attempt to
|
|
<<fast-forwards,fast-forward>> to the commit given by example.com's
|
|
master branch. In more detail:
|
|
|
|
[[fetch-fast-forwards]]
|
|
git fetch and fast-forwards
|
|
---------------------------
|
|
|
|
In the previous example, when updating an existing branch, `git fetch`
|
|
checks to make sure that the most recent commit on the remote
|
|
branch is a descendant of the most recent commit on your copy of the
|
|
branch before updating your copy of the branch to point at the new
|
|
commit. Git calls this process a <<fast-forwards,fast-forward>>.
|
|
|
|
A fast-forward looks something like this:
|
|
|
|
................................................
|
|
o--o--o--o <-- old head of the branch
|
|
\
|
|
o--o--o <-- new head of the branch
|
|
................................................
|
|
|
|
|
|
In some cases it is possible that the new head will *not* actually be
|
|
a descendant of the old head. For example, the developer may have
|
|
realized she made a serious mistake, and decided to backtrack,
|
|
resulting in a situation like:
|
|
|
|
................................................
|
|
o--o--o--o--a--b <-- old head of the branch
|
|
\
|
|
o--o--o <-- new head of the branch
|
|
................................................
|
|
|
|
In this case, `git fetch` will fail, and print out a warning.
|
|
|
|
In that case, you can still force Git to update to the new head, as
|
|
described in the following section. However, note that in the
|
|
situation above this may mean losing the commits labeled `a` and `b`,
|
|
unless you've already created a reference of your own pointing to
|
|
them.
|
|
|
|
[[forcing-fetch]]
|
|
Forcing git fetch to do non-fast-forward updates
|
|
------------------------------------------------
|
|
|
|
If git fetch fails because the new head of a branch is not a
|
|
descendant of the old head, you may force the update with:
|
|
|
|
-------------------------------------------------
|
|
$ git fetch git://example.com/proj.git +master:refs/remotes/example/master
|
|
-------------------------------------------------
|
|
|
|
Note the addition of the `+` sign. Alternatively, you can use the `-f`
|
|
flag to force updates of all the fetched branches, as in:
|
|
|
|
-------------------------------------------------
|
|
$ git fetch -f origin
|
|
-------------------------------------------------
|
|
|
|
Be aware that commits that the old version of example/master pointed at
|
|
may be lost, as we saw in the previous section.
|
|
|
|
[[remote-branch-configuration]]
|
|
Configuring remote-tracking branches
|
|
------------------------------------
|
|
|
|
We saw above that `origin` is just a shortcut to refer to the
|
|
repository that you originally cloned from. This information is
|
|
stored in Git configuration variables, which you can see using
|
|
linkgit:git-config[1]:
|
|
|
|
-------------------------------------------------
|
|
$ git config -l
|
|
core.repositoryformatversion=0
|
|
core.filemode=true
|
|
core.logallrefupdates=true
|
|
remote.origin.url=git://git.kernel.org/pub/scm/git/git.git
|
|
remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*
|
|
branch.master.remote=origin
|
|
branch.master.merge=refs/heads/master
|
|
-------------------------------------------------
|
|
|
|
If there are other repositories that you also use frequently, you can
|
|
create similar configuration options to save typing; for example,
|
|
|
|
-------------------------------------------------
|
|
$ git remote add example git://example.com/proj.git
|
|
-------------------------------------------------
|
|
|
|
adds the following to `.git/config`:
|
|
|
|
-------------------------------------------------
|
|
[remote "example"]
|
|
url = git://example.com/proj.git
|
|
fetch = +refs/heads/*:refs/remotes/example/*
|
|
-------------------------------------------------
|
|
|
|
Also note that the above configuration can be performed by directly
|
|
editing the file `.git/config` instead of using linkgit:git-remote[1].
|
|
|
|
After configuring the remote, the following three commands will do the
|
|
same thing:
|
|
|
|
-------------------------------------------------
|
|
$ git fetch git://example.com/proj.git +refs/heads/*:refs/remotes/example/*
|
|
$ git fetch example +refs/heads/*:refs/remotes/example/*
|
|
$ git fetch example
|
|
-------------------------------------------------
|
|
|
|
See linkgit:git-config[1] for more details on the configuration
|
|
options mentioned above and linkgit:git-fetch[1] for more details on
|
|
the refspec syntax.
|
|
|
|
|
|
[[git-concepts]]
|
|
Git concepts
|
|
============
|
|
|
|
Git is built on a small number of simple but powerful ideas. While it
|
|
is possible to get things done without understanding them, you will find
|
|
Git much more intuitive if you do.
|
|
|
|
We start with the most important, the <<def_object_database,object
|
|
database>> and the <<def_index,index>>.
|
|
|
|
[[the-object-database]]
|
|
The Object Database
|
|
-------------------
|
|
|
|
|
|
We already saw in <<understanding-commits>> that all commits are stored
|
|
under a 40-digit "object name". In fact, all the information needed to
|
|
represent the history of a project is stored in objects with such names.
|
|
In each case the name is calculated by taking the SHA-1 hash of the
|
|
contents of the object. The SHA-1 hash is a cryptographic hash function.
|
|
What that means to us is that it is impossible to find two different
|
|
objects with the same name. This has a number of advantages; among
|
|
others:
|
|
|
|
- Git can quickly determine whether two objects are identical or not,
|
|
just by comparing names.
|
|
- Since object names are computed the same way in every repository, the
|
|
same content stored in two repositories will always be stored under
|
|
the same name.
|
|
- Git can detect errors when it reads an object, by checking that the
|
|
object's name is still the SHA-1 hash of its contents.
|
|
|
|
(See <<object-details>> for the details of the object formatting and
|
|
SHA-1 calculation.)
|
|
|
|
There are four different types of objects: "blob", "tree", "commit", and
|
|
"tag".
|
|
|
|
- A <<def_blob_object,"blob" object>> is used to store file data.
|
|
- A <<def_tree_object,"tree" object>> ties one or more
|
|
"blob" objects into a directory structure. In addition, a tree object
|
|
can refer to other tree objects, thus creating a directory hierarchy.
|
|
- A <<def_commit_object,"commit" object>> ties such directory hierarchies
|
|
together into a <<def_DAG,directed acyclic graph>> of revisions--each
|
|
commit contains the object name of exactly one tree designating the
|
|
directory hierarchy at the time of the commit. In addition, a commit
|
|
refers to "parent" commit objects that describe the history of how we
|
|
arrived at that directory hierarchy.
|
|
- A <<def_tag_object,"tag" object>> symbolically identifies and can be
|
|
used to sign other objects. It contains the object name and type of
|
|
another object, a symbolic name (of course!) and, optionally, a
|
|
signature.
|
|
|
|
The object types in some more detail:
|
|
|
|
[[commit-object]]
|
|
Commit Object
|
|
~~~~~~~~~~~~~
|
|
|
|
The "commit" object links a physical state of a tree with a description
|
|
of how we got there and why. Use the `--pretty=raw` option to
|
|
linkgit:git-show[1] or linkgit:git-log[1] to examine your favorite
|
|
commit:
|
|
|
|
------------------------------------------------
|
|
$ git show -s --pretty=raw 2be7fcb476
|
|
commit 2be7fcb4764f2dbcee52635b91fedb1b3dcf7ab4
|
|
tree fb3a8bdd0ceddd019615af4d57a53f43d8cee2bf
|
|
parent 257a84d9d02e90447b149af58b271c19405edb6a
|
|
author Dave Watson <dwatson@mimvista.com> 1187576872 -0400
|
|
committer Junio C Hamano <gitster@pobox.com> 1187591163 -0700
|
|
|
|
Fix misspelling of 'suppress' in docs
|
|
|
|
Signed-off-by: Junio C Hamano <gitster@pobox.com>
|
|
------------------------------------------------
|
|
|
|
As you can see, a commit is defined by:
|
|
|
|
- a tree: The SHA-1 name of a tree object (as defined below), representing
|
|
the contents of a directory at a certain point in time.
|
|
- parent(s): The SHA-1 name(s) of some number of commits which represent the
|
|
immediately previous step(s) in the history of the project. The
|
|
example above has one parent; merge commits may have more than
|
|
one. A commit with no parents is called a "root" commit, and
|
|
represents the initial revision of a project. Each project must have
|
|
at least one root. A project can also have multiple roots, though
|
|
that isn't common (or necessarily a good idea).
|
|
- an author: The name of the person responsible for this change, together
|
|
with its date.
|
|
- a committer: The name of the person who actually created the commit,
|
|
with the date it was done. This may be different from the author, for
|
|
example, if the author was someone who wrote a patch and emailed it
|
|
to the person who used it to create the commit.
|
|
- a comment describing this commit.
|
|
|
|
Note that a commit does not itself contain any information about what
|
|
actually changed; all changes are calculated by comparing the contents
|
|
of the tree referred to by this commit with the trees associated with
|
|
its parents. In particular, Git does not attempt to record file renames
|
|
explicitly, though it can identify cases where the existence of the same
|
|
file data at changing paths suggests a rename. (See, for example, the
|
|
`-M` option to linkgit:git-diff[1]).
|
|
|
|
A commit is usually created by linkgit:git-commit[1], which creates a
|
|
commit whose parent is normally the current HEAD, and whose tree is
|
|
taken from the content currently stored in the index.
|
|
|
|
[[tree-object]]
|
|
Tree Object
|
|
~~~~~~~~~~~
|
|
|
|
The ever-versatile linkgit:git-show[1] command can also be used to
|
|
examine tree objects, but linkgit:git-ls-tree[1] will give you more
|
|
details:
|
|
|
|
------------------------------------------------
|
|
$ git ls-tree fb3a8bdd0ce
|
|
100644 blob 63c918c667fa005ff12ad89437f2fdc80926e21c .gitignore
|
|
100644 blob 5529b198e8d14decbe4ad99db3f7fb632de0439d .mailmap
|
|
100644 blob 6ff87c4664981e4397625791c8ea3bbb5f2279a3 COPYING
|
|
040000 tree 2fb783e477100ce076f6bf57e4a6f026013dc745 Documentation
|
|
100755 blob 3c0032cec592a765692234f1cba47dfdcc3a9200 GIT-VERSION-GEN
|
|
100644 blob 289b046a443c0647624607d471289b2c7dcd470b INSTALL
|
|
100644 blob 4eb463797adc693dc168b926b6932ff53f17d0b1 Makefile
|
|
100644 blob 548142c327a6790ff8821d67c2ee1eff7a656b52 README
|
|
...
|
|
------------------------------------------------
|
|
|
|
As you can see, a tree object contains a list of entries, each with a
|
|
mode, object type, SHA-1 name, and name, sorted by name. It represents
|
|
the contents of a single directory tree.
|
|
|
|
The object type may be a blob, representing the contents of a file, or
|
|
another tree, representing the contents of a subdirectory. Since trees
|
|
and blobs, like all other objects, are named by the SHA-1 hash of their
|
|
contents, two trees have the same SHA-1 name if and only if their
|
|
contents (including, recursively, the contents of all subdirectories)
|
|
are identical. This allows Git to quickly determine the differences
|
|
between two related tree objects, since it can ignore any entries with
|
|
identical object names.
|
|
|
|
(Note: in the presence of submodules, trees may also have commits as
|
|
entries. See <<submodules>> for documentation.)
|
|
|
|
Note that the files all have mode 644 or 755: Git actually only pays
|
|
attention to the executable bit.
|
|
|
|
[[blob-object]]
|
|
Blob Object
|
|
~~~~~~~~~~~
|
|
|
|
You can use linkgit:git-show[1] to examine the contents of a blob; take,
|
|
for example, the blob in the entry for `COPYING` from the tree above:
|
|
|
|
------------------------------------------------
|
|
$ git show 6ff87c4664
|
|
|
|
Note that the only valid version of the GPL as far as this project
|
|
is concerned is _this_ particular version of the license (ie v2, not
|
|
v2.2 or v3.x or whatever), unless explicitly otherwise stated.
|
|
...
|
|
------------------------------------------------
|
|
|
|
A "blob" object is nothing but a binary blob of data. It doesn't refer
|
|
to anything else or have attributes of any kind.
|
|
|
|
Since the blob is entirely defined by its data, if two files in a
|
|
directory tree (or in multiple different versions of the repository)
|
|
have the same contents, they will share the same blob object. The object
|
|
is totally independent of its location in the directory tree, and
|
|
renaming a file does not change the object that file is associated with.
|
|
|
|
Note that any tree or blob object can be examined using
|
|
linkgit:git-show[1] with the <revision>:<path> syntax. This can
|
|
sometimes be useful for browsing the contents of a tree that is not
|
|
currently checked out.
|
|
|
|
[[trust]]
|
|
Trust
|
|
~~~~~
|
|
|
|
If you receive the SHA-1 name of a blob from one source, and its contents
|
|
from another (possibly untrusted) source, you can still trust that those
|
|
contents are correct as long as the SHA-1 name agrees. This is because
|
|
the SHA-1 is designed so that it is infeasible to find different contents
|
|
that produce the same hash.
|
|
|
|
Similarly, you need only trust the SHA-1 name of a top-level tree object
|
|
to trust the contents of the entire directory that it refers to, and if
|
|
you receive the SHA-1 name of a commit from a trusted source, then you
|
|
can easily verify the entire history of commits reachable through
|
|
parents of that commit, and all of those contents of the trees referred
|
|
to by those commits.
|
|
|
|
So to introduce some real trust in the system, the only thing you need
|
|
to do is to digitally sign just 'one' special note, which includes the
|
|
name of a top-level commit. Your digital signature shows others
|
|
that you trust that commit, and the immutability of the history of
|
|
commits tells others that they can trust the whole history.
|
|
|
|
In other words, you can easily validate a whole archive by just
|
|
sending out a single email that tells the people the name (SHA-1 hash)
|
|
of the top commit, and digitally sign that email using something
|
|
like GPG/PGP.
|
|
|
|
To assist in this, Git also provides the tag object...
|
|
|
|
[[tag-object]]
|
|
Tag Object
|
|
~~~~~~~~~~
|
|
|
|
A tag object contains an object, object type, tag name, the name of the
|
|
person ("tagger") who created the tag, and a message, which may contain
|
|
a signature, as can be seen using linkgit:git-cat-file[1]:
|
|
|
|
------------------------------------------------
|
|
$ git cat-file tag v1.5.0
|
|
object 437b1b20df4b356c9342dac8d38849f24ef44f27
|
|
type commit
|
|
tag v1.5.0
|
|
tagger Junio C Hamano <junkio@cox.net> 1171411200 +0000
|
|
|
|
GIT 1.5.0
|
|
-----BEGIN PGP SIGNATURE-----
|
|
Version: GnuPG v1.4.6 (GNU/Linux)
|
|
|
|
iD8DBQBF0lGqwMbZpPMRm5oRAuRiAJ9ohBLd7s2kqjkKlq1qqC57SbnmzQCdG4ui
|
|
nLE/L9aUXdWeTFPron96DLA=
|
|
=2E+0
|
|
-----END PGP SIGNATURE-----
|
|
------------------------------------------------
|
|
|
|
See the linkgit:git-tag[1] command to learn how to create and verify tag
|
|
objects. (Note that linkgit:git-tag[1] can also be used to create
|
|
"lightweight tags", which are not tag objects at all, but just simple
|
|
references whose names begin with `refs/tags/`).
|
|
|
|
[[pack-files]]
|
|
How Git stores objects efficiently: pack files
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Newly created objects are initially created in a file named after the
|
|
object's SHA-1 hash (stored in `.git/objects`).
|
|
|
|
Unfortunately this system becomes inefficient once a project has a
|
|
lot of objects. Try this on an old project:
|
|
|
|
------------------------------------------------
|
|
$ git count-objects
|
|
6930 objects, 47620 kilobytes
|
|
------------------------------------------------
|
|
|
|
The first number is the number of objects which are kept in
|
|
individual files. The second is the amount of space taken up by
|
|
those "loose" objects.
|
|
|
|
You can save space and make Git faster by moving these loose objects in
|
|
to a "pack file", which stores a group of objects in an efficient
|
|
compressed format; the details of how pack files are formatted can be
|
|
found in link:technical/pack-format.txt[technical/pack-format.txt].
|
|
|
|
To put the loose objects into a pack, just run git repack:
|
|
|
|
------------------------------------------------
|
|
$ git repack
|
|
Generating pack...
|
|
Done counting 6020 objects.
|
|
Deltifying 6020 objects.
|
|
100% (6020/6020) done
|
|
Writing 6020 objects.
|
|
100% (6020/6020) done
|
|
Total 6020, written 6020 (delta 4070), reused 0 (delta 0)
|
|
Pack pack-3e54ad29d5b2e05838c75df582c65257b8d08e1c created.
|
|
------------------------------------------------
|
|
|
|
You can then run
|
|
|
|
------------------------------------------------
|
|
$ git prune
|
|
------------------------------------------------
|
|
|
|
to remove any of the "loose" objects that are now contained in the
|
|
pack. This will also remove any unreferenced objects (which may be
|
|
created when, for example, you use `git reset` to remove a commit).
|
|
You can verify that the loose objects are gone by looking at the
|
|
`.git/objects` directory or by running
|
|
|
|
------------------------------------------------
|
|
$ git count-objects
|
|
0 objects, 0 kilobytes
|
|
------------------------------------------------
|
|
|
|
Although the object files are gone, any commands that refer to those
|
|
objects will work exactly as they did before.
|
|
|
|
The linkgit:git-gc[1] command performs packing, pruning, and more for
|
|
you, so is normally the only high-level command you need.
|
|
|
|
[[dangling-objects]]
|
|
Dangling objects
|
|
~~~~~~~~~~~~~~~~
|
|
|
|
The linkgit:git-fsck[1] command will sometimes complain about dangling
|
|
objects. They are not a problem.
|
|
|
|
The most common cause of dangling objects is that you've rebased a
|
|
branch, or you have pulled from somebody else who rebased a branch--see
|
|
<<cleaning-up-history>>. In that case, the old head of the original
|
|
branch still exists, as does everything it pointed to. The branch
|
|
pointer itself just doesn't, since you replaced it with another one.
|
|
|
|
There are also other situations that cause dangling objects. For
|
|
example, a "dangling blob" may arise because you did a `git add` of a
|
|
file, but then, before you actually committed it and made it part of the
|
|
bigger picture, you changed something else in that file and committed
|
|
that *updated* thing--the old state that you added originally ends up
|
|
not being pointed to by any commit or tree, so it's now a dangling blob
|
|
object.
|
|
|
|
Similarly, when the "recursive" merge strategy runs, and finds that
|
|
there are criss-cross merges and thus more than one merge base (which is
|
|
fairly unusual, but it does happen), it will generate one temporary
|
|
midway tree (or possibly even more, if you had lots of criss-crossing
|
|
merges and more than two merge bases) as a temporary internal merge
|
|
base, and again, those are real objects, but the end result will not end
|
|
up pointing to them, so they end up "dangling" in your repository.
|
|
|
|
Generally, dangling objects aren't anything to worry about. They can
|
|
even be very useful: if you screw something up, the dangling objects can
|
|
be how you recover your old tree (say, you did a rebase, and realized
|
|
that you really didn't want to--you can look at what dangling objects
|
|
you have, and decide to reset your head to some old dangling state).
|
|
|
|
For commits, you can just use:
|
|
|
|
------------------------------------------------
|
|
$ gitk <dangling-commit-sha-goes-here> --not --all
|
|
------------------------------------------------
|
|
|
|
This asks for all the history reachable from the given commit but not
|
|
from any branch, tag, or other reference. If you decide it's something
|
|
you want, you can always create a new reference to it, e.g.,
|
|
|
|
------------------------------------------------
|
|
$ git branch recovered-branch <dangling-commit-sha-goes-here>
|
|
------------------------------------------------
|
|
|
|
For blobs and trees, you can't do the same, but you can still examine
|
|
them. You can just do
|
|
|
|
------------------------------------------------
|
|
$ git show <dangling-blob/tree-sha-goes-here>
|
|
------------------------------------------------
|
|
|
|
to show what the contents of the blob were (or, for a tree, basically
|
|
what the `ls` for that directory was), and that may give you some idea
|
|
of what the operation was that left that dangling object.
|
|
|
|
Usually, dangling blobs and trees aren't very interesting. They're
|
|
almost always the result of either being a half-way mergebase (the blob
|
|
will often even have the conflict markers from a merge in it, if you
|
|
have had conflicting merges that you fixed up by hand), or simply
|
|
because you interrupted a `git fetch` with ^C or something like that,
|
|
leaving _some_ of the new objects in the object database, but just
|
|
dangling and useless.
|
|
|
|
Anyway, once you are sure that you're not interested in any dangling
|
|
state, you can just prune all unreachable objects:
|
|
|
|
------------------------------------------------
|
|
$ git prune
|
|
------------------------------------------------
|
|
|
|
and they'll be gone. But you should only run `git prune` on a quiescent
|
|
repository--it's kind of like doing a filesystem fsck recovery: you
|
|
don't want to do that while the filesystem is mounted.
|
|
|
|
(The same is true of `git fsck` itself, btw, but since
|
|
`git fsck` never actually *changes* the repository, it just reports
|
|
on what it found, `git fsck` itself is never 'dangerous' to run.
|
|
Running it while somebody is actually changing the repository can cause
|
|
confusing and scary messages, but it won't actually do anything bad. In
|
|
contrast, running `git prune` while somebody is actively changing the
|
|
repository is a *BAD* idea).
|
|
|
|
[[recovering-from-repository-corruption]]
|
|
Recovering from repository corruption
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
By design, Git treats data trusted to it with caution. However, even in
|
|
the absence of bugs in Git itself, it is still possible that hardware or
|
|
operating system errors could corrupt data.
|
|
|
|
The first defense against such problems is backups. You can back up a
|
|
Git directory using clone, or just using cp, tar, or any other backup
|
|
mechanism.
|
|
|
|
As a last resort, you can search for the corrupted objects and attempt
|
|
to replace them by hand. Back up your repository before attempting this
|
|
in case you corrupt things even more in the process.
|
|
|
|
We'll assume that the problem is a single missing or corrupted blob,
|
|
which is sometimes a solvable problem. (Recovering missing trees and
|
|
especially commits is *much* harder).
|
|
|
|
Before starting, verify that there is corruption, and figure out where
|
|
it is with linkgit:git-fsck[1]; this may be time-consuming.
|
|
|
|
Assume the output looks like this:
|
|
|
|
------------------------------------------------
|
|
$ git fsck --full --no-dangling
|
|
broken link from tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8
|
|
to blob 4b9458b3786228369c63936db65827de3cc06200
|
|
missing blob 4b9458b3786228369c63936db65827de3cc06200
|
|
------------------------------------------------
|
|
|
|
Now you know that blob 4b9458b3 is missing, and that the tree 2d9263c6
|
|
points to it. If you could find just one copy of that missing blob
|
|
object, possibly in some other repository, you could move it into
|
|
`.git/objects/4b/9458b3...` and be done. Suppose you can't. You can
|
|
still examine the tree that pointed to it with linkgit:git-ls-tree[1],
|
|
which might output something like:
|
|
|
|
------------------------------------------------
|
|
$ git ls-tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8
|
|
100644 blob 8d14531846b95bfa3564b58ccfb7913a034323b8 .gitignore
|
|
100644 blob ebf9bf84da0aab5ed944264a5db2a65fe3a3e883 .mailmap
|
|
100644 blob ca442d313d86dc67e0a2e5d584b465bd382cbf5c COPYING
|
|
...
|
|
100644 blob 4b9458b3786228369c63936db65827de3cc06200 myfile
|
|
...
|
|
------------------------------------------------
|
|
|
|
So now you know that the missing blob was the data for a file named
|
|
`myfile`. And chances are you can also identify the directory--let's
|
|
say it's in `somedirectory`. If you're lucky the missing copy might be
|
|
the same as the copy you have checked out in your working tree at
|
|
`somedirectory/myfile`; you can test whether that's right with
|
|
linkgit:git-hash-object[1]:
|
|
|
|
------------------------------------------------
|
|
$ git hash-object -w somedirectory/myfile
|
|
------------------------------------------------
|
|
|
|
which will create and store a blob object with the contents of
|
|
somedirectory/myfile, and output the SHA-1 of that object. if you're
|
|
extremely lucky it might be 4b9458b3786228369c63936db65827de3cc06200, in
|
|
which case you've guessed right, and the corruption is fixed!
|
|
|
|
Otherwise, you need more information. How do you tell which version of
|
|
the file has been lost?
|
|
|
|
The easiest way to do this is with:
|
|
|
|
------------------------------------------------
|
|
$ git log --raw --all --full-history -- somedirectory/myfile
|
|
------------------------------------------------
|
|
|
|
Because you're asking for raw output, you'll now get something like
|
|
|
|
------------------------------------------------
|
|
commit abc
|
|
Author:
|
|
Date:
|
|
...
|
|
:100644 100644 4b9458b... newsha... M somedirectory/myfile
|
|
|
|
|
|
commit xyz
|
|
Author:
|
|
Date:
|
|
|
|
...
|
|
:100644 100644 oldsha... 4b9458b... M somedirectory/myfile
|
|
------------------------------------------------
|
|
|
|
This tells you that the immediately following version of the file was
|
|
"newsha", and that the immediately preceding version was "oldsha".
|
|
You also know the commit messages that went with the change from oldsha
|
|
to 4b9458b and with the change from 4b9458b to newsha.
|
|
|
|
If you've been committing small enough changes, you may now have a good
|
|
shot at reconstructing the contents of the in-between state 4b9458b.
|
|
|
|
If you can do that, you can now recreate the missing object with
|
|
|
|
------------------------------------------------
|
|
$ git hash-object -w <recreated-file>
|
|
------------------------------------------------
|
|
|
|
and your repository is good again!
|
|
|
|
(Btw, you could have ignored the `fsck`, and started with doing a
|
|
|
|
------------------------------------------------
|
|
$ git log --raw --all
|
|
------------------------------------------------
|
|
|
|
and just looked for the sha of the missing object (4b9458b..) in that
|
|
whole thing. It's up to you--Git does *have* a lot of information, it is
|
|
just missing one particular blob version.
|
|
|
|
[[the-index]]
|
|
The index
|
|
-----------
|
|
|
|
The index is a binary file (generally kept in `.git/index`) containing a
|
|
sorted list of path names, each with permissions and the SHA-1 of a blob
|
|
object; linkgit:git-ls-files[1] can show you the contents of the index:
|
|
|
|
-------------------------------------------------
|
|
$ git ls-files --stage
|
|
100644 63c918c667fa005ff12ad89437f2fdc80926e21c 0 .gitignore
|
|
100644 5529b198e8d14decbe4ad99db3f7fb632de0439d 0 .mailmap
|
|
100644 6ff87c4664981e4397625791c8ea3bbb5f2279a3 0 COPYING
|
|
100644 a37b2152bd26be2c2289e1f57a292534a51a93c7 0 Documentation/.gitignore
|
|
100644 fbefe9a45b00a54b58d94d06eca48b03d40a50e0 0 Documentation/Makefile
|
|
...
|
|
100644 2511aef8d89ab52be5ec6a5e46236b4b6bcd07ea 0 xdiff/xtypes.h
|
|
100644 2ade97b2574a9f77e7ae4002a4e07a6a38e46d07 0 xdiff/xutils.c
|
|
100644 d5de8292e05e7c36c4b68857c1cf9855e3d2f70a 0 xdiff/xutils.h
|
|
-------------------------------------------------
|
|
|
|
Note that in older documentation you may see the index called the
|
|
"current directory cache" or just the "cache". It has three important
|
|
properties:
|
|
|
|
1. The index contains all the information necessary to generate a single
|
|
(uniquely determined) tree object.
|
|
+
|
|
For example, running linkgit:git-commit[1] generates this tree object
|
|
from the index, stores it in the object database, and uses it as the
|
|
tree object associated with the new commit.
|
|
|
|
2. The index enables fast comparisons between the tree object it defines
|
|
and the working tree.
|
|
+
|
|
It does this by storing some additional data for each entry (such as
|
|
the last modified time). This data is not displayed above, and is not
|
|
stored in the created tree object, but it can be used to determine
|
|
quickly which files in the working directory differ from what was
|
|
stored in the index, and thus save Git from having to read all of the
|
|
data from such files to look for changes.
|
|
|
|
3. It can efficiently represent information about merge conflicts
|
|
between different tree objects, allowing each pathname to be
|
|
associated with sufficient information about the trees involved that
|
|
you can create a three-way merge between them.
|
|
+
|
|
We saw in <<conflict-resolution>> that during a merge the index can
|
|
store multiple versions of a single file (called "stages"). The third
|
|
column in the linkgit:git-ls-files[1] output above is the stage
|
|
number, and will take on values other than 0 for files with merge
|
|
conflicts.
|
|
|
|
The index is thus a sort of temporary staging area, which is filled with
|
|
a tree which you are in the process of working on.
|
|
|
|
If you blow the index away entirely, you generally haven't lost any
|
|
information as long as you have the name of the tree that it described.
|
|
|
|
[[submodules]]
|
|
Submodules
|
|
==========
|
|
|
|
Large projects are often composed of smaller, self-contained modules. For
|
|
example, an embedded Linux distribution's source tree would include every
|
|
piece of software in the distribution with some local modifications; a movie
|
|
player might need to build against a specific, known-working version of a
|
|
decompression library; several independent programs might all share the same
|
|
build scripts.
|
|
|
|
With centralized revision control systems this is often accomplished by
|
|
including every module in one single repository. Developers can check out
|
|
all modules or only the modules they need to work with. They can even modify
|
|
files across several modules in a single commit while moving things around
|
|
or updating APIs and translations.
|
|
|
|
Git does not allow partial checkouts, so duplicating this approach in Git
|
|
would force developers to keep a local copy of modules they are not
|
|
interested in touching. Commits in an enormous checkout would be slower
|
|
than you'd expect as Git would have to scan every directory for changes.
|
|
If modules have a lot of local history, clones would take forever.
|
|
|
|
On the plus side, distributed revision control systems can much better
|
|
integrate with external sources. In a centralized model, a single arbitrary
|
|
snapshot of the external project is exported from its own revision control
|
|
and then imported into the local revision control on a vendor branch. All
|
|
the history is hidden. With distributed revision control you can clone the
|
|
entire external history and much more easily follow development and re-merge
|
|
local changes.
|
|
|
|
Git's submodule support allows a repository to contain, as a subdirectory, a
|
|
checkout of an external project. Submodules maintain their own identity;
|
|
the submodule support just stores the submodule repository location and
|
|
commit ID, so other developers who clone the containing project
|
|
("superproject") can easily clone all the submodules at the same revision.
|
|
Partial checkouts of the superproject are possible: you can tell Git to
|
|
clone none, some or all of the submodules.
|
|
|
|
The linkgit:git-submodule[1] command is available since Git 1.5.3. Users
|
|
with Git 1.5.2 can look up the submodule commits in the repository and
|
|
manually check them out; earlier versions won't recognize the submodules at
|
|
all.
|
|
|
|
To see how submodule support works, create (for example) four example
|
|
repositories that can be used later as a submodule:
|
|
|
|
-------------------------------------------------
|
|
$ mkdir ~/git
|
|
$ cd ~/git
|
|
$ for i in a b c d
|
|
do
|
|
mkdir $i
|
|
cd $i
|
|
git init
|
|
echo "module $i" > $i.txt
|
|
git add $i.txt
|
|
git commit -m "Initial commit, submodule $i"
|
|
cd ..
|
|
done
|
|
-------------------------------------------------
|
|
|
|
Now create the superproject and add all the submodules:
|
|
|
|
-------------------------------------------------
|
|
$ mkdir super
|
|
$ cd super
|
|
$ git init
|
|
$ for i in a b c d
|
|
do
|
|
git submodule add ~/git/$i $i
|
|
done
|
|
-------------------------------------------------
|
|
|
|
NOTE: Do not use local URLs here if you plan to publish your superproject!
|
|
|
|
See what files `git submodule` created:
|
|
|
|
-------------------------------------------------
|
|
$ ls -a
|
|
. .. .git .gitmodules a b c d
|
|
-------------------------------------------------
|
|
|
|
The `git submodule add <repo> <path>` command does a couple of things:
|
|
|
|
- It clones the submodule from `<repo>` to the given `<path>` under the
|
|
current directory and by default checks out the master branch.
|
|
- It adds the submodule's clone path to the linkgit:gitmodules[5] file and
|
|
adds this file to the index, ready to be committed.
|
|
- It adds the submodule's current commit ID to the index, ready to be
|
|
committed.
|
|
|
|
Commit the superproject:
|
|
|
|
-------------------------------------------------
|
|
$ git commit -m "Add submodules a, b, c and d."
|
|
-------------------------------------------------
|
|
|
|
Now clone the superproject:
|
|
|
|
-------------------------------------------------
|
|
$ cd ..
|
|
$ git clone super cloned
|
|
$ cd cloned
|
|
-------------------------------------------------
|
|
|
|
The submodule directories are there, but they're empty:
|
|
|
|
-------------------------------------------------
|
|
$ ls -a a
|
|
. ..
|
|
$ git submodule status
|
|
-d266b9873ad50488163457f025db7cdd9683d88b a
|
|
-e81d457da15309b4fef4249aba9b50187999670d b
|
|
-c1536a972b9affea0f16e0680ba87332dc059146 c
|
|
-d96249ff5d57de5de093e6baff9e0aafa5276a74 d
|
|
-------------------------------------------------
|
|
|
|
NOTE: The commit object names shown above would be different for you, but they
|
|
should match the HEAD commit object names of your repositories. You can check
|
|
it by running `git ls-remote ../a`.
|
|
|
|
Pulling down the submodules is a two-step process. First run `git submodule
|
|
init` to add the submodule repository URLs to `.git/config`:
|
|
|
|
-------------------------------------------------
|
|
$ git submodule init
|
|
-------------------------------------------------
|
|
|
|
Now use `git submodule update` to clone the repositories and check out the
|
|
commits specified in the superproject:
|
|
|
|
-------------------------------------------------
|
|
$ git submodule update
|
|
$ cd a
|
|
$ ls -a
|
|
. .. .git a.txt
|
|
-------------------------------------------------
|
|
|
|
One major difference between `git submodule update` and `git submodule add` is
|
|
that `git submodule update` checks out a specific commit, rather than the tip
|
|
of a branch. It's like checking out a tag: the head is detached, so you're not
|
|
working on a branch.
|
|
|
|
-------------------------------------------------
|
|
$ git branch
|
|
* (no branch)
|
|
master
|
|
-------------------------------------------------
|
|
|
|
If you want to make a change within a submodule and you have a detached head,
|
|
then you should create or checkout a branch, make your changes, publish the
|
|
change within the submodule, and then update the superproject to reference the
|
|
new commit:
|
|
|
|
-------------------------------------------------
|
|
$ git checkout master
|
|
-------------------------------------------------
|
|
|
|
or
|
|
|
|
-------------------------------------------------
|
|
$ git checkout -b fix-up
|
|
-------------------------------------------------
|
|
|
|
then
|
|
|
|
-------------------------------------------------
|
|
$ echo "adding a line again" >> a.txt
|
|
$ git commit -a -m "Updated the submodule from within the superproject."
|
|
$ git push
|
|
$ cd ..
|
|
$ git diff
|
|
diff --git a/a b/a
|
|
index d266b98..261dfac 160000
|
|
--- a/a
|
|
+++ b/a
|
|
@@ -1 +1 @@
|
|
-Subproject commit d266b9873ad50488163457f025db7cdd9683d88b
|
|
+Subproject commit 261dfac35cb99d380eb966e102c1197139f7fa24
|
|
$ git add a
|
|
$ git commit -m "Updated submodule a."
|
|
$ git push
|
|
-------------------------------------------------
|
|
|
|
You have to run `git submodule update` after `git pull` if you want to update
|
|
submodules, too.
|
|
|
|
Pitfalls with submodules
|
|
------------------------
|
|
|
|
Always publish the submodule change before publishing the change to the
|
|
superproject that references it. If you forget to publish the submodule change,
|
|
others won't be able to clone the repository:
|
|
|
|
-------------------------------------------------
|
|
$ cd ~/git/super/a
|
|
$ echo i added another line to this file >> a.txt
|
|
$ git commit -a -m "doing it wrong this time"
|
|
$ cd ..
|
|
$ git add a
|
|
$ git commit -m "Updated submodule a again."
|
|
$ git push
|
|
$ cd ~/git/cloned
|
|
$ git pull
|
|
$ git submodule update
|
|
error: pathspec '261dfac35cb99d380eb966e102c1197139f7fa24' did not match any file(s) known to git.
|
|
Did you forget to 'git add'?
|
|
Unable to checkout '261dfac35cb99d380eb966e102c1197139f7fa24' in submodule path 'a'
|
|
-------------------------------------------------
|
|
|
|
In older Git versions it could be easily forgotten to commit new or modified
|
|
files in a submodule, which silently leads to similar problems as not pushing
|
|
the submodule changes. Starting with Git 1.7.0 both `git status` and `git diff`
|
|
in the superproject show submodules as modified when they contain new or
|
|
modified files to protect against accidentally committing such a state. `git
|
|
diff` will also add a `-dirty` to the work tree side when generating patch
|
|
output or used with the `--submodule` option:
|
|
|
|
-------------------------------------------------
|
|
$ git diff
|
|
diff --git a/sub b/sub
|
|
--- a/sub
|
|
+++ b/sub
|
|
@@ -1 +1 @@
|
|
-Subproject commit 3f356705649b5d566d97ff843cf193359229a453
|
|
+Subproject commit 3f356705649b5d566d97ff843cf193359229a453-dirty
|
|
$ git diff --submodule
|
|
Submodule sub 3f35670..3f35670-dirty:
|
|
-------------------------------------------------
|
|
|
|
You also should not rewind branches in a submodule beyond commits that were
|
|
ever recorded in any superproject.
|
|
|
|
It's not safe to run `git submodule update` if you've made and committed
|
|
changes within a submodule without checking out a branch first. They will be
|
|
silently overwritten:
|
|
|
|
-------------------------------------------------
|
|
$ cat a.txt
|
|
module a
|
|
$ echo line added from private2 >> a.txt
|
|
$ git commit -a -m "line added inside private2"
|
|
$ cd ..
|
|
$ git submodule update
|
|
Submodule path 'a': checked out 'd266b9873ad50488163457f025db7cdd9683d88b'
|
|
$ cd a
|
|
$ cat a.txt
|
|
module a
|
|
-------------------------------------------------
|
|
|
|
NOTE: The changes are still visible in the submodule's reflog.
|
|
|
|
If you have uncommitted changes in your submodule working tree, `git
|
|
submodule update` will not overwrite them. Instead, you get the usual
|
|
warning about not being able switch from a dirty branch.
|
|
|
|
[[low-level-operations]]
|
|
Low-level Git operations
|
|
========================
|
|
|
|
Many of the higher-level commands were originally implemented as shell
|
|
scripts using a smaller core of low-level Git commands. These can still
|
|
be useful when doing unusual things with Git, or just as a way to
|
|
understand its inner workings.
|
|
|
|
[[object-manipulation]]
|
|
Object access and manipulation
|
|
------------------------------
|
|
|
|
The linkgit:git-cat-file[1] command can show the contents of any object,
|
|
though the higher-level linkgit:git-show[1] is usually more useful.
|
|
|
|
The linkgit:git-commit-tree[1] command allows constructing commits with
|
|
arbitrary parents and trees.
|
|
|
|
A tree can be created with linkgit:git-write-tree[1] and its data can be
|
|
accessed by linkgit:git-ls-tree[1]. Two trees can be compared with
|
|
linkgit:git-diff-tree[1].
|
|
|
|
A tag is created with linkgit:git-mktag[1], and the signature can be
|
|
verified by linkgit:git-verify-tag[1], though it is normally simpler to
|
|
use linkgit:git-tag[1] for both.
|
|
|
|
[[the-workflow]]
|
|
The Workflow
|
|
------------
|
|
|
|
High-level operations such as linkgit:git-commit[1],
|
|
linkgit:git-checkout[1] and linkgit:git-reset[1] work by moving data
|
|
between the working tree, the index, and the object database. Git
|
|
provides low-level operations which perform each of these steps
|
|
individually.
|
|
|
|
Generally, all Git operations work on the index file. Some operations
|
|
work *purely* on the index file (showing the current state of the
|
|
index), but most operations move data between the index file and either
|
|
the database or the working directory. Thus there are four main
|
|
combinations:
|
|
|
|
[[working-directory-to-index]]
|
|
working directory -> index
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
The linkgit:git-update-index[1] command updates the index with
|
|
information from the working directory. You generally update the
|
|
index information by just specifying the filename you want to update,
|
|
like so:
|
|
|
|
-------------------------------------------------
|
|
$ git update-index filename
|
|
-------------------------------------------------
|
|
|
|
but to avoid common mistakes with filename globbing etc, the command
|
|
will not normally add totally new entries or remove old entries,
|
|
i.e. it will normally just update existing cache entries.
|
|
|
|
To tell Git that yes, you really do realize that certain files no
|
|
longer exist, or that new files should be added, you
|
|
should use the `--remove` and `--add` flags respectively.
|
|
|
|
NOTE! A `--remove` flag does 'not' mean that subsequent filenames will
|
|
necessarily be removed: if the files still exist in your directory
|
|
structure, the index will be updated with their new status, not
|
|
removed. The only thing `--remove` means is that update-index will be
|
|
considering a removed file to be a valid thing, and if the file really
|
|
does not exist any more, it will update the index accordingly.
|
|
|
|
As a special case, you can also do `git update-index --refresh`, which
|
|
will refresh the "stat" information of each index to match the current
|
|
stat information. It will 'not' update the object status itself, and
|
|
it will only update the fields that are used to quickly test whether
|
|
an object still matches its old backing store object.
|
|
|
|
The previously introduced linkgit:git-add[1] is just a wrapper for
|
|
linkgit:git-update-index[1].
|
|
|
|
[[index-to-object-database]]
|
|
index -> object database
|
|
~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
You write your current index file to a "tree" object with the program
|
|
|
|
-------------------------------------------------
|
|
$ git write-tree
|
|
-------------------------------------------------
|
|
|
|
that doesn't come with any options--it will just write out the
|
|
current index into the set of tree objects that describe that state,
|
|
and it will return the name of the resulting top-level tree. You can
|
|
use that tree to re-generate the index at any time by going in the
|
|
other direction:
|
|
|
|
[[object-database-to-index]]
|
|
object database -> index
|
|
~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
You read a "tree" file from the object database, and use that to
|
|
populate (and overwrite--don't do this if your index contains any
|
|
unsaved state that you might want to restore later!) your current
|
|
index. Normal operation is just
|
|
|
|
-------------------------------------------------
|
|
$ git read-tree <SHA-1 of tree>
|
|
-------------------------------------------------
|
|
|
|
and your index file will now be equivalent to the tree that you saved
|
|
earlier. However, that is only your 'index' file: your working
|
|
directory contents have not been modified.
|
|
|
|
[[index-to-working-directory]]
|
|
index -> working directory
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
You update your working directory from the index by "checking out"
|
|
files. This is not a very common operation, since normally you'd just
|
|
keep your files updated, and rather than write to your working
|
|
directory, you'd tell the index files about the changes in your
|
|
working directory (i.e. `git update-index`).
|
|
|
|
However, if you decide to jump to a new version, or check out somebody
|
|
else's version, or just restore a previous tree, you'd populate your
|
|
index file with read-tree, and then you need to check out the result
|
|
with
|
|
|
|
-------------------------------------------------
|
|
$ git checkout-index filename
|
|
-------------------------------------------------
|
|
|
|
or, if you want to check out all of the index, use `-a`.
|
|
|
|
NOTE! `git checkout-index` normally refuses to overwrite old files, so
|
|
if you have an old version of the tree already checked out, you will
|
|
need to use the `-f` flag ('before' the `-a` flag or the filename) to
|
|
'force' the checkout.
|
|
|
|
|
|
Finally, there are a few odds and ends which are not purely moving
|
|
from one representation to the other:
|
|
|
|
[[tying-it-all-together]]
|
|
Tying it all together
|
|
~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
To commit a tree you have instantiated with `git write-tree`, you'd
|
|
create a "commit" object that refers to that tree and the history
|
|
behind it--most notably the "parent" commits that preceded it in
|
|
history.
|
|
|
|
Normally a "commit" has one parent: the previous state of the tree
|
|
before a certain change was made. However, sometimes it can have two
|
|
or more parent commits, in which case we call it a "merge", due to the
|
|
fact that such a commit brings together ("merges") two or more
|
|
previous states represented by other commits.
|
|
|
|
In other words, while a "tree" represents a particular directory state
|
|
of a working directory, a "commit" represents that state in "time",
|
|
and explains how we got there.
|
|
|
|
You create a commit object by giving it the tree that describes the
|
|
state at the time of the commit, and a list of parents:
|
|
|
|
-------------------------------------------------
|
|
$ git commit-tree <tree> -p <parent> [(-p <parent2>)...]
|
|
-------------------------------------------------
|
|
|
|
and then giving the reason for the commit on stdin (either through
|
|
redirection from a pipe or file, or by just typing it at the tty).
|
|
|
|
`git commit-tree` will return the name of the object that represents
|
|
that commit, and you should save it away for later use. Normally,
|
|
you'd commit a new `HEAD` state, and while Git doesn't care where you
|
|
save the note about that state, in practice we tend to just write the
|
|
result to the file pointed at by `.git/HEAD`, so that we can always see
|
|
what the last committed state was.
|
|
|
|
Here is an ASCII art by Jon Loeliger that illustrates how
|
|
various pieces fit together.
|
|
|
|
------------
|
|
|
|
commit-tree
|
|
commit obj
|
|
+----+
|
|
| |
|
|
| |
|
|
V V
|
|
+-----------+
|
|
| Object DB |
|
|
| Backing |
|
|
| Store |
|
|
+-----------+
|
|
^
|
|
write-tree | |
|
|
tree obj | |
|
|
| | read-tree
|
|
| | tree obj
|
|
V
|
|
+-----------+
|
|
| Index |
|
|
| "cache" |
|
|
+-----------+
|
|
update-index ^
|
|
blob obj | |
|
|
| |
|
|
checkout-index -u | | checkout-index
|
|
stat | | blob obj
|
|
V
|
|
+-----------+
|
|
| Working |
|
|
| Directory |
|
|
+-----------+
|
|
|
|
------------
|
|
|
|
|
|
[[examining-the-data]]
|
|
Examining the data
|
|
------------------
|
|
|
|
You can examine the data represented in the object database and the
|
|
index with various helper tools. For every object, you can use
|
|
linkgit:git-cat-file[1] to examine details about the
|
|
object:
|
|
|
|
-------------------------------------------------
|
|
$ git cat-file -t <objectname>
|
|
-------------------------------------------------
|
|
|
|
shows the type of the object, and once you have the type (which is
|
|
usually implicit in where you find the object), you can use
|
|
|
|
-------------------------------------------------
|
|
$ git cat-file blob|tree|commit|tag <objectname>
|
|
-------------------------------------------------
|
|
|
|
to show its contents. NOTE! Trees have binary content, and as a result
|
|
there is a special helper for showing that content, called
|
|
`git ls-tree`, which turns the binary content into a more easily
|
|
readable form.
|
|
|
|
It's especially instructive to look at "commit" objects, since those
|
|
tend to be small and fairly self-explanatory. In particular, if you
|
|
follow the convention of having the top commit name in `.git/HEAD`,
|
|
you can do
|
|
|
|
-------------------------------------------------
|
|
$ git cat-file commit HEAD
|
|
-------------------------------------------------
|
|
|
|
to see what the top commit was.
|
|
|
|
[[merging-multiple-trees]]
|
|
Merging multiple trees
|
|
----------------------
|
|
|
|
Git helps you do a three-way merge, which you can expand to n-way by
|
|
repeating the merge procedure arbitrary times until you finally
|
|
"commit" the state. The normal situation is that you'd only do one
|
|
three-way merge (two parents), and commit it, but if you like to, you
|
|
can do multiple parents in one go.
|
|
|
|
To do a three-way merge, you need the two sets of "commit" objects
|
|
that you want to merge, use those to find the closest common parent (a
|
|
third "commit" object), and then use those commit objects to find the
|
|
state of the directory ("tree" object) at these points.
|
|
|
|
To get the "base" for the merge, you first look up the common parent
|
|
of two commits with
|
|
|
|
-------------------------------------------------
|
|
$ git merge-base <commit1> <commit2>
|
|
-------------------------------------------------
|
|
|
|
which will return you the commit they are both based on. You should
|
|
now look up the "tree" objects of those commits, which you can easily
|
|
do with (for example)
|
|
|
|
-------------------------------------------------
|
|
$ git cat-file commit <commitname> | head -1
|
|
-------------------------------------------------
|
|
|
|
since the tree object information is always the first line in a commit
|
|
object.
|
|
|
|
Once you know the three trees you are going to merge (the one "original"
|
|
tree, aka the common tree, and the two "result" trees, aka the branches
|
|
you want to merge), you do a "merge" read into the index. This will
|
|
complain if it has to throw away your old index contents, so you should
|
|
make sure that you've committed those--in fact you would normally
|
|
always do a merge against your last commit (which should thus match what
|
|
you have in your current index anyway).
|
|
|
|
To do the merge, do
|
|
|
|
-------------------------------------------------
|
|
$ git read-tree -m -u <origtree> <yourtree> <targettree>
|
|
-------------------------------------------------
|
|
|
|
which will do all trivial merge operations for you directly in the
|
|
index file, and you can just write the result out with
|
|
`git write-tree`.
|
|
|
|
|
|
[[merging-multiple-trees-2]]
|
|
Merging multiple trees, continued
|
|
---------------------------------
|
|
|
|
Sadly, many merges aren't trivial. If there are files that have
|
|
been added, moved or removed, or if both branches have modified the
|
|
same file, you will be left with an index tree that contains "merge
|
|
entries" in it. Such an index tree can 'NOT' be written out to a tree
|
|
object, and you will have to resolve any such merge clashes using
|
|
other tools before you can write out the result.
|
|
|
|
You can examine such index state with `git ls-files --unmerged`
|
|
command. An example:
|
|
|
|
------------------------------------------------
|
|
$ git read-tree -m $orig HEAD $target
|
|
$ git ls-files --unmerged
|
|
100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello.c
|
|
100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello.c
|
|
100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello.c
|
|
------------------------------------------------
|
|
|
|
Each line of the `git ls-files --unmerged` output begins with
|
|
the blob mode bits, blob SHA-1, 'stage number', and the
|
|
filename. The 'stage number' is Git's way to say which tree it
|
|
came from: stage 1 corresponds to the `$orig` tree, stage 2 to
|
|
the `HEAD` tree, and stage 3 to the `$target` tree.
|
|
|
|
Earlier we said that trivial merges are done inside
|
|
`git read-tree -m`. For example, if the file did not change
|
|
from `$orig` to `HEAD` nor `$target`, or if the file changed
|
|
from `$orig` to `HEAD` and `$orig` to `$target` the same way,
|
|
obviously the final outcome is what is in `HEAD`. What the
|
|
above example shows is that file `hello.c` was changed from
|
|
`$orig` to `HEAD` and `$orig` to `$target` in a different way.
|
|
You could resolve this by running your favorite 3-way merge
|
|
program, e.g. `diff3`, `merge`, or Git's own merge-file, on
|
|
the blob objects from these three stages yourself, like this:
|
|
|
|
------------------------------------------------
|
|
$ git cat-file blob 263414f... >hello.c~1
|
|
$ git cat-file blob 06fa6a2... >hello.c~2
|
|
$ git cat-file blob cc44c73... >hello.c~3
|
|
$ git merge-file hello.c~2 hello.c~1 hello.c~3
|
|
------------------------------------------------
|
|
|
|
This would leave the merge result in `hello.c~2` file, along
|
|
with conflict markers if there are conflicts. After verifying
|
|
the merge result makes sense, you can tell Git what the final
|
|
merge result for this file is by:
|
|
|
|
-------------------------------------------------
|
|
$ mv -f hello.c~2 hello.c
|
|
$ git update-index hello.c
|
|
-------------------------------------------------
|
|
|
|
When a path is in the "unmerged" state, running `git update-index` for
|
|
that path tells Git to mark the path resolved.
|
|
|
|
The above is the description of a Git merge at the lowest level,
|
|
to help you understand what conceptually happens under the hood.
|
|
In practice, nobody, not even Git itself, runs `git cat-file` three times
|
|
for this. There is a `git merge-index` program that extracts the
|
|
stages to temporary files and calls a "merge" script on it:
|
|
|
|
-------------------------------------------------
|
|
$ git merge-index git-merge-one-file hello.c
|
|
-------------------------------------------------
|
|
|
|
and that is what higher level `git merge -s resolve` is implemented with.
|
|
|
|
[[hacking-git]]
|
|
Hacking Git
|
|
===========
|
|
|
|
This chapter covers internal details of the Git implementation which
|
|
probably only Git developers need to understand.
|
|
|
|
[[object-details]]
|
|
Object storage format
|
|
---------------------
|
|
|
|
All objects have a statically determined "type" which identifies the
|
|
format of the object (i.e. how it is used, and how it can refer to other
|
|
objects). There are currently four different object types: "blob",
|
|
"tree", "commit", and "tag".
|
|
|
|
Regardless of object type, all objects share the following
|
|
characteristics: they are all deflated with zlib, and have a header
|
|
that not only specifies their type, but also provides size information
|
|
about the data in the object. It's worth noting that the SHA-1 hash
|
|
that is used to name the object is the hash of the original data
|
|
plus this header, so `sha1sum` 'file' does not match the object name
|
|
for 'file'.
|
|
(Historical note: in the dawn of the age of Git the hash
|
|
was the SHA-1 of the 'compressed' object.)
|
|
|
|
As a result, the general consistency of an object can always be tested
|
|
independently of the contents or the type of the object: all objects can
|
|
be validated by verifying that (a) their hashes match the content of the
|
|
file and (b) the object successfully inflates to a stream of bytes that
|
|
forms a sequence of
|
|
`<ascii type without space> + <space> + <ascii decimal size> +
|
|
<byte\0> + <binary object data>`.
|
|
|
|
The structured objects can further have their structure and
|
|
connectivity to other objects verified. This is generally done with
|
|
the `git fsck` program, which generates a full dependency graph
|
|
of all objects, and verifies their internal consistency (in addition
|
|
to just verifying their superficial consistency through the hash).
|
|
|
|
[[birdview-on-the-source-code]]
|
|
A birds-eye view of Git's source code
|
|
-------------------------------------
|
|
|
|
It is not always easy for new developers to find their way through Git's
|
|
source code. This section gives you a little guidance to show where to
|
|
start.
|
|
|
|
A good place to start is with the contents of the initial commit, with:
|
|
|
|
----------------------------------------------------
|
|
$ git checkout e83c5163
|
|
----------------------------------------------------
|
|
|
|
The initial revision lays the foundation for almost everything Git has
|
|
today, but is small enough to read in one sitting.
|
|
|
|
Note that terminology has changed since that revision. For example, the
|
|
README in that revision uses the word "changeset" to describe what we
|
|
now call a <<def_commit_object,commit>>.
|
|
|
|
Also, we do not call it "cache" any more, but rather "index"; however, the
|
|
file is still called `cache.h`. Remark: Not much reason to change it now,
|
|
especially since there is no good single name for it anyway, because it is
|
|
basically _the_ header file which is included by _all_ of Git's C sources.
|
|
|
|
If you grasp the ideas in that initial commit, you should check out a
|
|
more recent version and skim `cache.h`, `object.h` and `commit.h`.
|
|
|
|
In the early days, Git (in the tradition of UNIX) was a bunch of programs
|
|
which were extremely simple, and which you used in scripts, piping the
|
|
output of one into another. This turned out to be good for initial
|
|
development, since it was easier to test new things. However, recently
|
|
many of these parts have become builtins, and some of the core has been
|
|
"libified", i.e. put into libgit.a for performance, portability reasons,
|
|
and to avoid code duplication.
|
|
|
|
By now, you know what the index is (and find the corresponding data
|
|
structures in `cache.h`), and that there are just a couple of object types
|
|
(blobs, trees, commits and tags) which inherit their common structure from
|
|
`struct object`, which is their first member (and thus, you can cast e.g.
|
|
`(struct object *)commit` to achieve the _same_ as `&commit->object`, i.e.
|
|
get at the object name and flags).
|
|
|
|
Now is a good point to take a break to let this information sink in.
|
|
|
|
Next step: get familiar with the object naming. Read <<naming-commits>>.
|
|
There are quite a few ways to name an object (and not only revisions!).
|
|
All of these are handled in `sha1_name.c`. Just have a quick look at
|
|
the function `get_sha1()`. A lot of the special handling is done by
|
|
functions like `get_sha1_basic()` or the likes.
|
|
|
|
This is just to get you into the groove for the most libified part of Git:
|
|
the revision walker.
|
|
|
|
Basically, the initial version of `git log` was a shell script:
|
|
|
|
----------------------------------------------------------------
|
|
$ git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | \
|
|
LESS=-S ${PAGER:-less}
|
|
----------------------------------------------------------------
|
|
|
|
What does this mean?
|
|
|
|
`git rev-list` is the original version of the revision walker, which
|
|
_always_ printed a list of revisions to stdout. It is still functional,
|
|
and needs to, since most new Git commands start out as scripts using
|
|
`git rev-list`.
|
|
|
|
`git rev-parse` is not as important any more; it was only used to filter out
|
|
options that were relevant for the different plumbing commands that were
|
|
called by the script.
|
|
|
|
Most of what `git rev-list` did is contained in `revision.c` and
|
|
`revision.h`. It wraps the options in a struct named `rev_info`, which
|
|
controls how and what revisions are walked, and more.
|
|
|
|
The original job of `git rev-parse` is now taken by the function
|
|
`setup_revisions()`, which parses the revisions and the common command line
|
|
options for the revision walker. This information is stored in the struct
|
|
`rev_info` for later consumption. You can do your own command line option
|
|
parsing after calling `setup_revisions()`. After that, you have to call
|
|
`prepare_revision_walk()` for initialization, and then you can get the
|
|
commits one by one with the function `get_revision()`.
|
|
|
|
If you are interested in more details of the revision walking process,
|
|
just have a look at the first implementation of `cmd_log()`; call
|
|
`git show v1.3.0~155^2~4` and scroll down to that function (note that you
|
|
no longer need to call `setup_pager()` directly).
|
|
|
|
Nowadays, `git log` is a builtin, which means that it is _contained_ in the
|
|
command `git`. The source side of a builtin is
|
|
|
|
- a function called `cmd_<bla>`, typically defined in `builtin-<bla>.c`,
|
|
and declared in `builtin.h`,
|
|
|
|
- an entry in the `commands[]` array in `git.c`, and
|
|
|
|
- an entry in `BUILTIN_OBJECTS` in the `Makefile`.
|
|
|
|
Sometimes, more than one builtin is contained in one source file. For
|
|
example, `cmd_whatchanged()` and `cmd_log()` both reside in `builtin-log.c`,
|
|
since they share quite a bit of code. In that case, the commands which are
|
|
_not_ named like the `.c` file in which they live have to be listed in
|
|
`BUILT_INS` in the `Makefile`.
|
|
|
|
`git log` looks more complicated in C than it does in the original script,
|
|
but that allows for a much greater flexibility and performance.
|
|
|
|
Here again it is a good point to take a pause.
|
|
|
|
Lesson three is: study the code. Really, it is the best way to learn about
|
|
the organization of Git (after you know the basic concepts).
|
|
|
|
So, think about something which you are interested in, say, "how can I
|
|
access a blob just knowing the object name of it?". The first step is to
|
|
find a Git command with which you can do it. In this example, it is either
|
|
`git show` or `git cat-file`.
|
|
|
|
For the sake of clarity, let's stay with `git cat-file`, because it
|
|
|
|
- is plumbing, and
|
|
|
|
- was around even in the initial commit (it literally went only through
|
|
some 20 revisions as `cat-file.c`, was renamed to `builtin-cat-file.c`
|
|
when made a builtin, and then saw less than 10 versions).
|
|
|
|
So, look into `builtin-cat-file.c`, search for `cmd_cat_file()` and look what
|
|
it does.
|
|
|
|
------------------------------------------------------------------
|
|
git_config(git_default_config);
|
|
if (argc != 3)
|
|
usage("git cat-file [-t|-s|-e|-p|<type>] <sha1>");
|
|
if (get_sha1(argv[2], sha1))
|
|
die("Not a valid object name %s", argv[2]);
|
|
------------------------------------------------------------------
|
|
|
|
Let's skip over the obvious details; the only really interesting part
|
|
here is the call to `get_sha1()`. It tries to interpret `argv[2]` as an
|
|
object name, and if it refers to an object which is present in the current
|
|
repository, it writes the resulting SHA-1 into the variable `sha1`.
|
|
|
|
Two things are interesting here:
|
|
|
|
- `get_sha1()` returns 0 on _success_. This might surprise some new
|
|
Git hackers, but there is a long tradition in UNIX to return different
|
|
negative numbers in case of different errors--and 0 on success.
|
|
|
|
- the variable `sha1` in the function signature of `get_sha1()` is `unsigned
|
|
char *`, but is actually expected to be a pointer to `unsigned
|
|
char[20]`. This variable will contain the 160-bit SHA-1 of the given
|
|
commit. Note that whenever a SHA-1 is passed as `unsigned char *`, it
|
|
is the binary representation, as opposed to the ASCII representation in
|
|
hex characters, which is passed as `char *`.
|
|
|
|
You will see both of these things throughout the code.
|
|
|
|
Now, for the meat:
|
|
|
|
-----------------------------------------------------------------------------
|
|
case 0:
|
|
buf = read_object_with_reference(sha1, argv[1], &size, NULL);
|
|
-----------------------------------------------------------------------------
|
|
|
|
This is how you read a blob (actually, not only a blob, but any type of
|
|
object). To know how the function `read_object_with_reference()` actually
|
|
works, find the source code for it (something like `git grep
|
|
read_object_with | grep ":[a-z]"` in the Git repository), and read
|
|
the source.
|
|
|
|
To find out how the result can be used, just read on in `cmd_cat_file()`:
|
|
|
|
-----------------------------------
|
|
write_or_die(1, buf, size);
|
|
-----------------------------------
|
|
|
|
Sometimes, you do not know where to look for a feature. In many such cases,
|
|
it helps to search through the output of `git log`, and then `git show` the
|
|
corresponding commit.
|
|
|
|
Example: If you know that there was some test case for `git bundle`, but
|
|
do not remember where it was (yes, you _could_ `git grep bundle t/`, but that
|
|
does not illustrate the point!):
|
|
|
|
------------------------
|
|
$ git log --no-merges t/
|
|
------------------------
|
|
|
|
In the pager (`less`), just search for "bundle", go a few lines back,
|
|
and see that it is in commit 18449ab0... Now just copy this object name,
|
|
and paste it into the command line
|
|
|
|
-------------------
|
|
$ git show 18449ab0
|
|
-------------------
|
|
|
|
Voila.
|
|
|
|
Another example: Find out what to do in order to make some script a
|
|
builtin:
|
|
|
|
-------------------------------------------------
|
|
$ git log --no-merges --diff-filter=A builtin-*.c
|
|
-------------------------------------------------
|
|
|
|
You see, Git is actually the best tool to find out about the source of Git
|
|
itself!
|
|
|
|
[[glossary]]
|
|
Git Glossary
|
|
============
|
|
|
|
include::glossary-content.txt[]
|
|
|
|
[[git-quick-start]]
|
|
Appendix A: Git Quick Reference
|
|
===============================
|
|
|
|
This is a quick summary of the major commands; the previous chapters
|
|
explain how these work in more detail.
|
|
|
|
[[quick-creating-a-new-repository]]
|
|
Creating a new repository
|
|
-------------------------
|
|
|
|
From a tarball:
|
|
|
|
-----------------------------------------------
|
|
$ tar xzf project.tar.gz
|
|
$ cd project
|
|
$ git init
|
|
Initialized empty Git repository in .git/
|
|
$ git add .
|
|
$ git commit
|
|
-----------------------------------------------
|
|
|
|
From a remote repository:
|
|
|
|
-----------------------------------------------
|
|
$ git clone git://example.com/pub/project.git
|
|
$ cd project
|
|
-----------------------------------------------
|
|
|
|
[[managing-branches]]
|
|
Managing branches
|
|
-----------------
|
|
|
|
-----------------------------------------------
|
|
$ git branch # list all local branches in this repo
|
|
$ git checkout test # switch working directory to branch "test"
|
|
$ git branch new # create branch "new" starting at current HEAD
|
|
$ git branch -d new # delete branch "new"
|
|
-----------------------------------------------
|
|
|
|
Instead of basing a new branch on current HEAD (the default), use:
|
|
|
|
-----------------------------------------------
|
|
$ git branch new test # branch named "test"
|
|
$ git branch new v2.6.15 # tag named v2.6.15
|
|
$ git branch new HEAD^ # commit before the most recent
|
|
$ git branch new HEAD^^ # commit before that
|
|
$ git branch new test~10 # ten commits before tip of branch "test"
|
|
-----------------------------------------------
|
|
|
|
Create and switch to a new branch at the same time:
|
|
|
|
-----------------------------------------------
|
|
$ git checkout -b new v2.6.15
|
|
-----------------------------------------------
|
|
|
|
Update and examine branches from the repository you cloned from:
|
|
|
|
-----------------------------------------------
|
|
$ git fetch # update
|
|
$ git branch -r # list
|
|
origin/master
|
|
origin/next
|
|
...
|
|
$ git checkout -b masterwork origin/master
|
|
-----------------------------------------------
|
|
|
|
Fetch a branch from a different repository, and give it a new
|
|
name in your repository:
|
|
|
|
-----------------------------------------------
|
|
$ git fetch git://example.com/project.git theirbranch:mybranch
|
|
$ git fetch git://example.com/project.git v2.6.15:mybranch
|
|
-----------------------------------------------
|
|
|
|
Keep a list of repositories you work with regularly:
|
|
|
|
-----------------------------------------------
|
|
$ git remote add example git://example.com/project.git
|
|
$ git remote # list remote repositories
|
|
example
|
|
origin
|
|
$ git remote show example # get details
|
|
* remote example
|
|
URL: git://example.com/project.git
|
|
Tracked remote branches
|
|
master
|
|
next
|
|
...
|
|
$ git fetch example # update branches from example
|
|
$ git branch -r # list all remote branches
|
|
-----------------------------------------------
|
|
|
|
|
|
[[exploring-history]]
|
|
Exploring history
|
|
-----------------
|
|
|
|
-----------------------------------------------
|
|
$ gitk # visualize and browse history
|
|
$ git log # list all commits
|
|
$ git log src/ # ...modifying src/
|
|
$ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15
|
|
$ git log master..test # ...in branch test, not in branch master
|
|
$ git log test..master # ...in branch master, but not in test
|
|
$ git log test...master # ...in one branch, not in both
|
|
$ git log -S'foo()' # ...where difference contain "foo()"
|
|
$ git log --since="2 weeks ago"
|
|
$ git log -p # show patches as well
|
|
$ git show # most recent commit
|
|
$ git diff v2.6.15..v2.6.16 # diff between two tagged versions
|
|
$ git diff v2.6.15..HEAD # diff with current head
|
|
$ git grep "foo()" # search working directory for "foo()"
|
|
$ git grep v2.6.15 "foo()" # search old tree for "foo()"
|
|
$ git show v2.6.15:a.txt # look at old version of a.txt
|
|
-----------------------------------------------
|
|
|
|
Search for regressions:
|
|
|
|
-----------------------------------------------
|
|
$ git bisect start
|
|
$ git bisect bad # current version is bad
|
|
$ git bisect good v2.6.13-rc2 # last known good revision
|
|
Bisecting: 675 revisions left to test after this
|
|
# test here, then:
|
|
$ git bisect good # if this revision is good, or
|
|
$ git bisect bad # if this revision is bad.
|
|
# repeat until done.
|
|
-----------------------------------------------
|
|
|
|
[[making-changes]]
|
|
Making changes
|
|
--------------
|
|
|
|
Make sure Git knows who to blame:
|
|
|
|
------------------------------------------------
|
|
$ cat >>~/.gitconfig <<\EOF
|
|
[user]
|
|
name = Your Name Comes Here
|
|
email = you@yourdomain.example.com
|
|
EOF
|
|
------------------------------------------------
|
|
|
|
Select file contents to include in the next commit, then make the
|
|
commit:
|
|
|
|
-----------------------------------------------
|
|
$ git add a.txt # updated file
|
|
$ git add b.txt # new file
|
|
$ git rm c.txt # old file
|
|
$ git commit
|
|
-----------------------------------------------
|
|
|
|
Or, prepare and create the commit in one step:
|
|
|
|
-----------------------------------------------
|
|
$ git commit d.txt # use latest content only of d.txt
|
|
$ git commit -a # use latest content of all tracked files
|
|
-----------------------------------------------
|
|
|
|
[[merging]]
|
|
Merging
|
|
-------
|
|
|
|
-----------------------------------------------
|
|
$ git merge test # merge branch "test" into the current branch
|
|
$ git pull git://example.com/project.git master
|
|
# fetch and merge in remote branch
|
|
$ git pull . test # equivalent to git merge test
|
|
-----------------------------------------------
|
|
|
|
[[sharing-your-changes]]
|
|
Sharing your changes
|
|
--------------------
|
|
|
|
Importing or exporting patches:
|
|
|
|
-----------------------------------------------
|
|
$ git format-patch origin..HEAD # format a patch for each commit
|
|
# in HEAD but not in origin
|
|
$ git am mbox # import patches from the mailbox "mbox"
|
|
-----------------------------------------------
|
|
|
|
Fetch a branch in a different Git repository, then merge into the
|
|
current branch:
|
|
|
|
-----------------------------------------------
|
|
$ git pull git://example.com/project.git theirbranch
|
|
-----------------------------------------------
|
|
|
|
Store the fetched branch into a local branch before merging into the
|
|
current branch:
|
|
|
|
-----------------------------------------------
|
|
$ git pull git://example.com/project.git theirbranch:mybranch
|
|
-----------------------------------------------
|
|
|
|
After creating commits on a local branch, update the remote
|
|
branch with your commits:
|
|
|
|
-----------------------------------------------
|
|
$ git push ssh://example.com/project.git mybranch:theirbranch
|
|
-----------------------------------------------
|
|
|
|
When remote and local branch are both named "test":
|
|
|
|
-----------------------------------------------
|
|
$ git push ssh://example.com/project.git test
|
|
-----------------------------------------------
|
|
|
|
Shortcut version for a frequently used remote repository:
|
|
|
|
-----------------------------------------------
|
|
$ git remote add example ssh://example.com/project.git
|
|
$ git push example test
|
|
-----------------------------------------------
|
|
|
|
[[repository-maintenance]]
|
|
Repository maintenance
|
|
----------------------
|
|
|
|
Check for corruption:
|
|
|
|
-----------------------------------------------
|
|
$ git fsck
|
|
-----------------------------------------------
|
|
|
|
Recompress, remove unused cruft:
|
|
|
|
-----------------------------------------------
|
|
$ git gc
|
|
-----------------------------------------------
|
|
|
|
|
|
[[todo]]
|
|
Appendix B: Notes and todo list for this manual
|
|
===============================================
|
|
|
|
This is a work in progress.
|
|
|
|
The basic requirements:
|
|
|
|
- It must be readable in order, from beginning to end, by someone
|
|
intelligent with a basic grasp of the UNIX command line, but without
|
|
any special knowledge of Git. If necessary, any other prerequisites
|
|
should be specifically mentioned as they arise.
|
|
- Whenever possible, section headings should clearly describe the task
|
|
they explain how to do, in language that requires no more knowledge
|
|
than necessary: for example, "importing patches into a project" rather
|
|
than "the `git am` command"
|
|
|
|
Think about how to create a clear chapter dependency graph that will
|
|
allow people to get to important topics without necessarily reading
|
|
everything in between.
|
|
|
|
Scan `Documentation/` for other stuff left out; in particular:
|
|
|
|
- howto's
|
|
- some of `technical/`?
|
|
- hooks
|
|
- list of commands in linkgit:git[1]
|
|
|
|
Scan email archives for other stuff left out
|
|
|
|
Scan man pages to see if any assume more background than this manual
|
|
provides.
|
|
|
|
Simplify beginning by suggesting disconnected head instead of
|
|
temporary branch creation?
|
|
|
|
Add more good examples. Entire sections of just cookbook examples
|
|
might be a good idea; maybe make an "advanced examples" section a
|
|
standard end-of-chapter section?
|
|
|
|
Include cross-references to the glossary, where appropriate.
|
|
|
|
Document shallow clones? See draft 1.5.0 release notes for some
|
|
documentation.
|
|
|
|
Add a section on working with other version control systems, including
|
|
CVS, Subversion, and just imports of series of release tarballs.
|
|
|
|
More details on gitweb?
|
|
|
|
Write a chapter on using plumbing and writing scripts.
|
|
|
|
Alternates, clone -reference, etc.
|
|
|
|
More on recovery from repository corruption. See:
|
|
http://marc.theaimsgroup.com/?l=git&m=117263864820799&w=2
|
|
http://marc.theaimsgroup.com/?l=git&m=117147855503798&w=2
|