mirror of
https://github.com/git/git.git
synced 2024-10-31 06:17:56 +01:00
24c512803d
This enhances the support for bisecting history in bare repositories. The "git bisect" command no longer needs to be run inside a repository with a working tree; it defaults to --no-checkout when run in a bare repository. Two tests are included to demonstrate this behaviour. Suggested-by: Junio C Hamano <gitster@pobox.com> Reviewed-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Jon Seymour <jon.seymour@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
385 lines
12 KiB
Text
385 lines
12 KiB
Text
git-bisect(1)
|
|
=============
|
|
|
|
NAME
|
|
----
|
|
git-bisect - Find by binary search the change that introduced a bug
|
|
|
|
|
|
SYNOPSIS
|
|
--------
|
|
[verse]
|
|
'git bisect' <subcommand> <options>
|
|
|
|
DESCRIPTION
|
|
-----------
|
|
The command takes various subcommands, and different options depending
|
|
on the subcommand:
|
|
|
|
git bisect help
|
|
git bisect start [--no-checkout] [<bad> [<good>...]] [--] [<paths>...]
|
|
git bisect bad [<rev>]
|
|
git bisect good [<rev>...]
|
|
git bisect skip [(<rev>|<range>)...]
|
|
git bisect reset [<commit>]
|
|
git bisect visualize
|
|
git bisect replay <logfile>
|
|
git bisect log
|
|
git bisect run <cmd>...
|
|
|
|
This command uses 'git rev-list --bisect' to help drive the
|
|
binary search process to find which change introduced a bug, given an
|
|
old "good" commit object name and a later "bad" commit object name.
|
|
|
|
Getting help
|
|
~~~~~~~~~~~~
|
|
|
|
Use "git bisect" to get a short usage description, and "git bisect
|
|
help" or "git bisect -h" to get a long usage description.
|
|
|
|
Basic bisect commands: start, bad, good
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Using the Linux kernel tree as an example, basic use of the bisect
|
|
command is as follows:
|
|
|
|
------------------------------------------------
|
|
$ git bisect start
|
|
$ git bisect bad # Current version is bad
|
|
$ git bisect good v2.6.13-rc2 # v2.6.13-rc2 was the last version
|
|
# tested that was good
|
|
------------------------------------------------
|
|
|
|
When you have specified at least one bad and one good version, the
|
|
command bisects the revision tree and outputs something similar to
|
|
the following:
|
|
|
|
------------------------------------------------
|
|
Bisecting: 675 revisions left to test after this
|
|
------------------------------------------------
|
|
|
|
The state in the middle of the set of revisions is then checked out.
|
|
You would now compile that kernel and boot it. If the booted kernel
|
|
works correctly, you would then issue the following command:
|
|
|
|
------------------------------------------------
|
|
$ git bisect good # this one is good
|
|
------------------------------------------------
|
|
|
|
The output of this command would be something similar to the following:
|
|
|
|
------------------------------------------------
|
|
Bisecting: 337 revisions left to test after this
|
|
------------------------------------------------
|
|
|
|
You keep repeating this process, compiling the tree, testing it, and
|
|
depending on whether it is good or bad issuing the command "git bisect good"
|
|
or "git bisect bad" to ask for the next bisection.
|
|
|
|
Eventually there will be no more revisions left to bisect, and you
|
|
will have been left with the first bad kernel revision in "refs/bisect/bad".
|
|
|
|
Bisect reset
|
|
~~~~~~~~~~~~
|
|
|
|
After a bisect session, to clean up the bisection state and return to
|
|
the original HEAD, issue the following command:
|
|
|
|
------------------------------------------------
|
|
$ git bisect reset
|
|
------------------------------------------------
|
|
|
|
By default, this will return your tree to the commit that was checked
|
|
out before `git bisect start`. (A new `git bisect start` will also do
|
|
that, as it cleans up the old bisection state.)
|
|
|
|
With an optional argument, you can return to a different commit
|
|
instead:
|
|
|
|
------------------------------------------------
|
|
$ git bisect reset <commit>
|
|
------------------------------------------------
|
|
|
|
For example, `git bisect reset HEAD` will leave you on the current
|
|
bisection commit and avoid switching commits at all, while `git bisect
|
|
reset bisect/bad` will check out the first bad revision.
|
|
|
|
Bisect visualize
|
|
~~~~~~~~~~~~~~~~
|
|
|
|
To see the currently remaining suspects in 'gitk', issue the following
|
|
command during the bisection process:
|
|
|
|
------------
|
|
$ git bisect visualize
|
|
------------
|
|
|
|
`view` may also be used as a synonym for `visualize`.
|
|
|
|
If the 'DISPLAY' environment variable is not set, 'git log' is used
|
|
instead. You can also give command line options such as `-p` and
|
|
`--stat`.
|
|
|
|
------------
|
|
$ git bisect view --stat
|
|
------------
|
|
|
|
Bisect log and bisect replay
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
After having marked revisions as good or bad, issue the following
|
|
command to show what has been done so far:
|
|
|
|
------------
|
|
$ git bisect log
|
|
------------
|
|
|
|
If you discover that you made a mistake in specifying the status of a
|
|
revision, you can save the output of this command to a file, edit it to
|
|
remove the incorrect entries, and then issue the following commands to
|
|
return to a corrected state:
|
|
|
|
------------
|
|
$ git bisect reset
|
|
$ git bisect replay that-file
|
|
------------
|
|
|
|
Avoiding testing a commit
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
If, in the middle of a bisect session, you know that the next suggested
|
|
revision is not a good one to test (e.g. the change the commit
|
|
introduces is known not to work in your environment and you know it
|
|
does not have anything to do with the bug you are chasing), you may
|
|
want to find a nearby commit and try that instead.
|
|
|
|
For example:
|
|
|
|
------------
|
|
$ git bisect good/bad # previous round was good or bad.
|
|
Bisecting: 337 revisions left to test after this
|
|
$ git bisect visualize # oops, that is uninteresting.
|
|
$ git reset --hard HEAD~3 # try 3 revisions before what
|
|
# was suggested
|
|
------------
|
|
|
|
Then compile and test the chosen revision, and afterwards mark
|
|
the revision as good or bad in the usual manner.
|
|
|
|
Bisect skip
|
|
~~~~~~~~~~~~
|
|
|
|
Instead of choosing by yourself a nearby commit, you can ask git
|
|
to do it for you by issuing the command:
|
|
|
|
------------
|
|
$ git bisect skip # Current version cannot be tested
|
|
------------
|
|
|
|
But git may eventually be unable to tell the first bad commit among
|
|
a bad commit and one or more skipped commits.
|
|
|
|
You can even skip a range of commits, instead of just one commit,
|
|
using the "'<commit1>'..'<commit2>'" notation. For example:
|
|
|
|
------------
|
|
$ git bisect skip v2.5..v2.6
|
|
------------
|
|
|
|
This tells the bisect process that no commit after `v2.5`, up to and
|
|
including `v2.6`, should be tested.
|
|
|
|
Note that if you also want to skip the first commit of the range you
|
|
would issue the command:
|
|
|
|
------------
|
|
$ git bisect skip v2.5 v2.5..v2.6
|
|
------------
|
|
|
|
This tells the bisect process that the commits between `v2.5` included
|
|
and `v2.6` included should be skipped.
|
|
|
|
|
|
Cutting down bisection by giving more parameters to bisect start
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
You can further cut down the number of trials, if you know what part of
|
|
the tree is involved in the problem you are tracking down, by specifying
|
|
path parameters when issuing the `bisect start` command:
|
|
|
|
------------
|
|
$ git bisect start -- arch/i386 include/asm-i386
|
|
------------
|
|
|
|
If you know beforehand more than one good commit, you can narrow the
|
|
bisect space down by specifying all of the good commits immediately after
|
|
the bad commit when issuing the `bisect start` command:
|
|
|
|
------------
|
|
$ git bisect start v2.6.20-rc6 v2.6.20-rc4 v2.6.20-rc1 --
|
|
# v2.6.20-rc6 is bad
|
|
# v2.6.20-rc4 and v2.6.20-rc1 are good
|
|
------------
|
|
|
|
Bisect run
|
|
~~~~~~~~~~
|
|
|
|
If you have a script that can tell if the current source code is good
|
|
or bad, you can bisect by issuing the command:
|
|
|
|
------------
|
|
$ git bisect run my_script arguments
|
|
------------
|
|
|
|
Note that the script (`my_script` in the above example) should
|
|
exit with code 0 if the current source code is good, and exit with a
|
|
code between 1 and 127 (inclusive), except 125, if the current
|
|
source code is bad.
|
|
|
|
Any other exit code will abort the bisect process. It should be noted
|
|
that a program that terminates via "exit(-1)" leaves $? = 255, (see the
|
|
exit(3) manual page), as the value is chopped with "& 0377".
|
|
|
|
The special exit code 125 should be used when the current source code
|
|
cannot be tested. If the script exits with this code, the current
|
|
revision will be skipped (see `git bisect skip` above). 125 was chosen
|
|
as the highest sensible value to use for this purpose, because 126 and 127
|
|
are used by POSIX shells to signal specific error status (127 is for
|
|
command not found, 126 is for command found but not executable---these
|
|
details do not matter, as they are normal errors in the script, as far as
|
|
"bisect run" is concerned).
|
|
|
|
You may often find that during a bisect session you want to have
|
|
temporary modifications (e.g. s/#define DEBUG 0/#define DEBUG 1/ in a
|
|
header file, or "revision that does not have this commit needs this
|
|
patch applied to work around another problem this bisection is not
|
|
interested in") applied to the revision being tested.
|
|
|
|
To cope with such a situation, after the inner 'git bisect' finds the
|
|
next revision to test, the script can apply the patch
|
|
before compiling, run the real test, and afterwards decide if the
|
|
revision (possibly with the needed patch) passed the test and then
|
|
rewind the tree to the pristine state. Finally the script should exit
|
|
with the status of the real test to let the "git bisect run" command loop
|
|
determine the eventual outcome of the bisect session.
|
|
|
|
OPTIONS
|
|
-------
|
|
--no-checkout::
|
|
+
|
|
Do not checkout the new working tree at each iteration of the bisection
|
|
process. Instead just update a special reference named 'BISECT_HEAD' to make
|
|
it point to the commit that should be tested.
|
|
+
|
|
This option may be useful when the test you would perform in each step
|
|
does not require a checked out tree.
|
|
+
|
|
If the repository is bare, `--no-checkout` is assumed.
|
|
|
|
EXAMPLES
|
|
--------
|
|
|
|
* Automatically bisect a broken build between v1.2 and HEAD:
|
|
+
|
|
------------
|
|
$ git bisect start HEAD v1.2 -- # HEAD is bad, v1.2 is good
|
|
$ git bisect run make # "make" builds the app
|
|
------------
|
|
|
|
* Automatically bisect a test failure between origin and HEAD:
|
|
+
|
|
------------
|
|
$ git bisect start HEAD origin -- # HEAD is bad, origin is good
|
|
$ git bisect run make test # "make test" builds and tests
|
|
------------
|
|
|
|
* Automatically bisect a broken test case:
|
|
+
|
|
------------
|
|
$ cat ~/test.sh
|
|
#!/bin/sh
|
|
make || exit 125 # this skips broken builds
|
|
~/check_test_case.sh # does the test case pass?
|
|
$ git bisect start HEAD HEAD~10 -- # culprit is among the last 10
|
|
$ git bisect run ~/test.sh
|
|
------------
|
|
+
|
|
Here we use a "test.sh" custom script. In this script, if "make"
|
|
fails, we skip the current commit.
|
|
"check_test_case.sh" should "exit 0" if the test case passes,
|
|
and "exit 1" otherwise.
|
|
+
|
|
It is safer if both "test.sh" and "check_test_case.sh" are
|
|
outside the repository to prevent interactions between the bisect,
|
|
make and test processes and the scripts.
|
|
|
|
* Automatically bisect with temporary modifications (hot-fix):
|
|
+
|
|
------------
|
|
$ cat ~/test.sh
|
|
#!/bin/sh
|
|
|
|
# tweak the working tree by merging the hot-fix branch
|
|
# and then attempt a build
|
|
if git merge --no-commit hot-fix &&
|
|
make
|
|
then
|
|
# run project specific test and report its status
|
|
~/check_test_case.sh
|
|
status=$?
|
|
else
|
|
# tell the caller this is untestable
|
|
status=125
|
|
fi
|
|
|
|
# undo the tweak to allow clean flipping to the next commit
|
|
git reset --hard
|
|
|
|
# return control
|
|
exit $status
|
|
------------
|
|
+
|
|
This applies modifications from a hot-fix branch before each test run,
|
|
e.g. in case your build or test environment changed so that older
|
|
revisions may need a fix which newer ones have already. (Make sure the
|
|
hot-fix branch is based off a commit which is contained in all revisions
|
|
which you are bisecting, so that the merge does not pull in too much, or
|
|
use `git cherry-pick` instead of `git merge`.)
|
|
|
|
* Automatically bisect a broken test case:
|
|
+
|
|
------------
|
|
$ git bisect start HEAD HEAD~10 -- # culprit is among the last 10
|
|
$ git bisect run sh -c "make || exit 125; ~/check_test_case.sh"
|
|
------------
|
|
+
|
|
This shows that you can do without a run script if you write the test
|
|
on a single line.
|
|
|
|
* Locate a good region of the object graph in a damaged repository
|
|
+
|
|
------------
|
|
$ git bisect start HEAD <known-good-commit> [ <boundary-commit> ... ] --no-checkout
|
|
$ git bisect run sh -c '
|
|
GOOD=$(git for-each-ref "--format=%(objectname)" refs/bisect/good-*) &&
|
|
git rev-list --objects BISECT_HEAD --not $GOOD >tmp.$$ &&
|
|
git pack-objects --stdout >/dev/null <tmp.$$
|
|
rc=$?
|
|
rm -f tmp.$$
|
|
test $rc = 0'
|
|
|
|
------------
|
|
+
|
|
In this case, when 'git bisect run' finishes, bisect/bad will refer to a commit that
|
|
has at least one parent whose reachable graph is fully traversable in the sense
|
|
required by 'git pack objects'.
|
|
|
|
|
|
SEE ALSO
|
|
--------
|
|
link:git-bisect-lk2009.html[Fighting regressions with git bisect],
|
|
linkgit:git-blame[1].
|
|
|
|
GIT
|
|
---
|
|
Part of the linkgit:git[1] suite
|