The current `update` command incorporates the superproject's gitlinked
SHA-1 ($sha1) into the submodule HEAD ($subsha1). Depending on the
options you use, it may checkout $sha1, rebase the $subsha1 onto
$sha1, or merge $sha1 into $subsha1. This helps you keep up with
changes in the upstream superproject.
However, it's also useful to stay up to date with changes in the
upstream subproject. Previous workflows for incorporating such
changes include the ungainly:
$ git submodule foreach 'git checkout $(git config --file $toplevel/.gitmodules submodule.$name.branch) && git pull'
With this patch, all of the useful functionality for incorporating
superproject changes can be reused to incorporate upstream subproject
updates. When you specify --remote, the target $sha1 is replaced with
a $sha1 of the submodule's origin/master tracking branch. If you want
to merge a different tracking branch, you can configure the
`submodule.<name>.branch` option in `.gitmodules`. You can override
the `.gitmodules` configuration setting for a particular superproject
by configuring the option in that superproject's default configuration
(using the usual configuration hierarchy, e.g. `.git/config`,
`~/.gitconfig`, etc.).
Previous use of submodule.<name>.branch
=======================================
Because we're adding a new configuration option, it's a good idea to
check if anyone else is already using the option. The foreach-pull
example above was described by Ævar in
commit f030c96d86
Author: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Fri May 21 16:10:10 2010 +0000
git-submodule foreach: Add $toplevel variable
Gerrit uses the same interpretation for the setting, but because
Gerrit has direct access to the subproject repositories, it updates
the superproject repositories automatically when a subproject changes.
Gerrit also accepts the special value '.', which it expands into the
superproject's branch name.
Although the --remote functionality is using `submodule.<name>.branch`
slightly differently, the effect is the same. The foreach-pull
example uses the option to record the name of the local branch to
checkout before pulls. The tracking branch to be pulled is recorded
in `.git/modules/<name>/config`, which was initialized by the module
clone during `submodule add` or `submodule init`. Because the branch
name stored in `submodule.<name>.branch` was likely the same as the
branch name used during the initial `submodule add`, the same branch
will be pulled in each workflow.
Implementation details
======================
In order to ensure a current tracking branch state, `update --remote`
fetches the submodule's remote repository before calculating the
SHA-1. However, I didn't change the logic guarding the existing fetch:
if test -z "$nofetch"
then
# Run fetch only if $sha1 isn't present or it
# is not reachable from a ref.
(clear_local_git_env; cd "$path" &&
( (rev=$(git rev-list -n 1 $sha1 --not --all 2>/dev/null) &&
test -z "$rev") || git-fetch)) ||
die "$(eval_gettext "Unable to fetch in submodule path '\$path'")"
fi
There will not be a double-fetch, because the new $sha1 determined
after the `--remote` triggered fetch should always exist in the
repository. If it doesn't, it's because some racy process removed it
from the submodule's repository and we *should* be re-fetching.
Signed-off-by: W. Trevor King <wking@tremily.us>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
////////////////////////////////////////////////////////////////
GIT - the stupid content tracker
////////////////////////////////////////////////////////////////
"git" can mean anything, depending on your mood.
- random three-letter combination that is pronounceable, and not
actually used by any common UNIX command. The fact that it is a
mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the
dictionary of slang.
- "global information tracker": you're in a good mood, and it actually
works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks
Git is a fast, scalable, distributed revision control system with an
unusually rich command set that provides both high-level operations
and full access to internals.
Git is an Open Source project covered by the GNU General Public License.
It was originally written by Linus Torvalds with help of a group of
hackers around the net. It is currently maintained by Junio C Hamano.
Please read the file INSTALL for installation instructions.
See Documentation/gittutorial.txt to get started, then see
Documentation/everyday.txt for a useful minimum set of commands, and
Documentation/git-commandname.txt for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with "man gittutorial" or "git help tutorial", and the
documentation of each command with "man git-commandname" or "git help
commandname".
CVS users may also want to read Documentation/gitcvs-migration.txt
("man gitcvs-migration" or "git help cvs-migration" if git is
installed).
Many Git online resources are accessible from http://git-scm.com/
including full documentation and Git related tools.
The user discussion and development of Git take place on the Git
mailing list -- everyone is welcome to post bug reports, feature
requests, comments and patches to git@vger.kernel.org (read
Documentation/SubmittingPatches for instructions on patch submission).
To subscribe to the list, send an email with just "subscribe git" in
the body to majordomo@vger.kernel.org. The mailing list archives are
available at http://marc.theaimsgroup.com/?l=git and other archival
sites.
The messages titled "A note from the maintainer", "What's in
git.git (stable)" and "What's cooking in git.git (topics)" and
the discussion following them on the mailing list give a good
reference for project status, development direction and
remaining tasks.
06b1abb5bd