19fa5e8c4d
These were added by accident in a42dea3.
This patch also rewords the description of how ranges of commits can be
skipped.
Signed-off-by: David J. Mellor <dmellor@whistlingcat.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
310 lines
9.5 KiB
Plaintext
310 lines
9.5 KiB
Plaintext
git-bisect(1)
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=============
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NAME
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----
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git-bisect - Find by binary search the change that introduced a bug
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SYNOPSIS
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--------
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'git bisect' <subcommand> <options>
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DESCRIPTION
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-----------
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The command takes various subcommands, and different options depending
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on the subcommand:
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git bisect help
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git bisect start [<bad> [<good>...]] [--] [<paths>...]
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git bisect bad [<rev>]
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git bisect good [<rev>...]
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git bisect skip [(<rev>|<range>)...]
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git bisect reset [<branch>]
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git bisect visualize
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git bisect replay <logfile>
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git bisect log
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git bisect run <cmd>...
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This command uses 'git rev-list --bisect' to help drive the
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binary search process to find which change introduced a bug, given an
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old "good" commit object name and a later "bad" commit object name.
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Getting help
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~~~~~~~~~~~~
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Use "git bisect" to get a short usage description, and "git bisect
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help" or "git bisect -h" to get a long usage description.
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Basic bisect commands: start, bad, good
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Using the Linux kernel tree as an example, basic use of the bisect
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command is as follows:
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------------------------------------------------
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$ git bisect start
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$ git bisect bad # Current version is bad
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$ git bisect good v2.6.13-rc2 # v2.6.13-rc2 was the last version
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# tested that was good
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------------------------------------------------
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When you have specified at least one bad and one good version, the
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command bisects the revision tree and outputs something similar to
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the following:
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------------------------------------------------
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Bisecting: 675 revisions left to test after this
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------------------------------------------------
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The state in the middle of the set of revisions is then checked out.
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You would now compile that kernel and boot it. If the booted kernel
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works correctly, you would then issue the following command:
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------------------------------------------------
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$ git bisect good # this one is good
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------------------------------------------------
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The output of this command would be something similar to the following:
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------------------------------------------------
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Bisecting: 337 revisions left to test after this
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------------------------------------------------
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You keep repeating this process, compiling the tree, testing it, and
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depending on whether it is good or bad issuing the command "git bisect good"
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or "git bisect bad" to ask for the next bisection.
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Eventually there will be no more revisions left to bisect, and you
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will have been left with the first bad kernel revision in "refs/bisect/bad".
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Bisect reset
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~~~~~~~~~~~~
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To return to the original head after a bisect session, issue the
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following command:
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------------------------------------------------
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$ git bisect reset
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------------------------------------------------
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This resets the tree to the original branch instead of being on the
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bisection commit ("git bisect start" will also do that, as it resets
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the bisection state).
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Bisect visualize
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~~~~~~~~~~~~~~~~
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To see the currently remaining suspects in 'gitk', issue the following
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command during the bisection process:
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------------
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$ git bisect visualize
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------------
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`view` may also be used as a synonym for `visualize`.
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If the 'DISPLAY' environment variable is not set, 'git log' is used
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instead. You can also give command line options such as `-p` and
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`--stat`.
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------------
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$ git bisect view --stat
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------------
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Bisect log and bisect replay
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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After having marked revisions as good or bad, issue the following
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command to show what has been done so far:
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------------
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$ git bisect log
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------------
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If you discover that you made a mistake in specifying the status of a
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revision, you can save the output of this command to a file, edit it to
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remove the incorrect entries, and then issue the following commands to
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return to a corrected state:
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------------
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$ git bisect reset
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$ git bisect replay that-file
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------------
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Avoiding testing a commit
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~~~~~~~~~~~~~~~~~~~~~~~~~
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If, in the middle of a bisect session, you know that the next suggested
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revision is not a good one to test (e.g. the change the commit
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introduces is known not to work in your environment and you know it
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does not have anything to do with the bug you are chasing), you may
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want to find a nearby commit and try that instead.
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For example:
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------------
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$ git bisect good/bad # previous round was good or bad.
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Bisecting: 337 revisions left to test after this
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$ git bisect visualize # oops, that is uninteresting.
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$ git reset --hard HEAD~3 # try 3 revisions before what
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# was suggested
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------------
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Then compile and test the chosen revision, and afterwards mark
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the revision as good or bad in the usual manner.
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Bisect skip
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~~~~~~~~~~~~
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Instead of choosing by yourself a nearby commit, you can ask git
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to do it for you by issuing the command:
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------------
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$ git bisect skip # Current version cannot be tested
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------------
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But computing the commit to test may be slower afterwards and git may
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eventually not be able to tell the first bad commit among a bad commit
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and one or more skipped commits.
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You can even skip a range of commits, instead of just one commit,
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using the "'<commit1>'..'<commit2>'" notation. For example:
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------------
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$ git bisect skip v2.5..v2.6
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------------
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This tells the bisect process that no commit after `v2.5`, up to and
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including `v2.6`, should be tested.
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Note that if you also want to skip the first commit of the range you
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would issue the command:
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------------
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$ git bisect skip v2.5 v2.5..v2.6
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------------
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This tells the bisect process that the commits between `v2.5` included
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and `v2.6` included should be skipped.
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Cutting down bisection by giving more parameters to bisect start
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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You can further cut down the number of trials, if you know what part of
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the tree is involved in the problem you are tracking down, by specifying
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path parameters when issuing the `bisect start` command:
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------------
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$ git bisect start -- arch/i386 include/asm-i386
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------------
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If you know beforehand more than one good commit, you can narrow the
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bisect space down by specifying all of the good commits immediately after
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the bad commit when issuing the `bisect start` command:
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------------
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$ git bisect start v2.6.20-rc6 v2.6.20-rc4 v2.6.20-rc1 --
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# v2.6.20-rc6 is bad
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# v2.6.20-rc4 and v2.6.20-rc1 are good
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------------
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Bisect run
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~~~~~~~~~~
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If you have a script that can tell if the current source code is good
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or bad, you can bisect by issuing the command:
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------------
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$ git bisect run my_script
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------------
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Note that the script (`my_script` in the above example) should
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exit with code 0 if the current source code is good, and exit with a
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code between 1 and 127 (inclusive), except 125, if the current
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source code is bad.
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Any other exit code will abort the bisect process. It should be noted
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that a program that terminates via "exit(-1)" leaves $? = 255, (see the
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exit(3) manual page), as the value is chopped with "& 0377".
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The special exit code 125 should be used when the current source code
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cannot be tested. If the script exits with this code, the current
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revision will be skipped (see `git bisect skip` above).
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You may often find that during a bisect session you want to have
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temporary modifications (e.g. s/#define DEBUG 0/#define DEBUG 1/ in a
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header file, or "revision that does not have this commit needs this
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patch applied to work around another problem this bisection is not
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interested in") applied to the revision being tested.
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To cope with such a situation, after the inner 'git bisect' finds the
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next revision to test, the script can apply the patch
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before compiling, run the real test, and afterwards decide if the
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revision (possibly with the needed patch) passed the test and then
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rewind the tree to the pristine state. Finally the script should exit
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with the status of the real test to let the "git bisect run" command loop
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determine the eventual outcome of the bisect session.
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EXAMPLES
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--------
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* Automatically bisect a broken build between v1.2 and HEAD:
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+
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------------
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$ git bisect start HEAD v1.2 -- # HEAD is bad, v1.2 is good
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$ git bisect run make # "make" builds the app
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------------
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* Automatically bisect a broken test suite:
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+
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------------
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$ cat ~/test.sh
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#!/bin/sh
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make || exit 125 # this skips broken builds
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make test # "make test" runs the test suite
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$ git bisect start v1.3 v1.1 -- # v1.3 is bad, v1.1 is good
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$ git bisect run ~/test.sh
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------------
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+
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Here we use a "test.sh" custom script. In this script, if "make"
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fails, we skip the current commit.
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+
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It is safer to use a custom script outside the repository to prevent
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interactions between the bisect, make and test processes and the
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script.
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+
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"make test" should "exit 0", if the test suite passes, and
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"exit 1" otherwise.
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* Automatically bisect a broken test case:
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+
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------------
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$ cat ~/test.sh
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#!/bin/sh
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make || exit 125 # this skips broken builds
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~/check_test_case.sh # does the test case passes ?
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$ git bisect start HEAD HEAD~10 -- # culprit is among the last 10
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$ git bisect run ~/test.sh
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------------
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+
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Here "check_test_case.sh" should "exit 0" if the test case passes,
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and "exit 1" otherwise.
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+
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It is safer if both "test.sh" and "check_test_case.sh" scripts are
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outside the repository to prevent interactions between the bisect,
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make and test processes and the scripts.
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Author
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------
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Written by Linus Torvalds <torvalds@osdl.org>
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Documentation
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-------------
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Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>.
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GIT
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---
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Part of the linkgit:git[1] suite
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