e8861ffc20
Upon seeing a merge commit when bisecting, this option may be used to follow only the first parent. In detecting regressions introduced through the merging of a branch, the merge commit will be identified as introduction of the bug and its ancestors will be ignored. This option is particularly useful in avoiding false positives when a merged branch contained broken or non-buildable commits, but the merge itself was OK. Signed-off-by: Aaron Lipman <alipman88@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
511 lines
17 KiB
Plaintext
511 lines
17 KiB
Plaintext
git-bisect(1)
|
|
=============
|
|
|
|
NAME
|
|
----
|
|
git-bisect - Use binary search to find the commit 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 start [--term-{old,good}=<term> --term-{new,bad}=<term>]
|
|
[--no-checkout] [--first-parent] [<bad> [<good>...]] [--] [<paths>...]
|
|
git bisect (bad|new|<term-new>) [<rev>]
|
|
git bisect (good|old|<term-old>) [<rev>...]
|
|
git bisect terms [--term-good | --term-bad]
|
|
git bisect skip [(<rev>|<range>)...]
|
|
git bisect reset [<commit>]
|
|
git bisect (visualize|view)
|
|
git bisect replay <logfile>
|
|
git bisect log
|
|
git bisect run <cmd>...
|
|
git bisect help
|
|
|
|
This command uses a binary search algorithm to find which commit in
|
|
your project's history introduced a bug. You use it by first telling
|
|
it a "bad" commit that is known to contain the bug, and a "good"
|
|
commit that is known to be before the bug was introduced. Then `git
|
|
bisect` picks a commit between those two endpoints and asks you
|
|
whether the selected commit is "good" or "bad". It continues narrowing
|
|
down the range until it finds the exact commit that introduced the
|
|
change.
|
|
|
|
In fact, `git bisect` can be used to find the commit that changed
|
|
*any* property of your project; e.g., the commit that fixed a bug, or
|
|
the commit that caused a benchmark's performance to improve. To
|
|
support this more general usage, the terms "old" and "new" can be used
|
|
in place of "good" and "bad", or you can choose your own terms. See
|
|
section "Alternate terms" below for more information.
|
|
|
|
Basic bisect commands: start, bad, good
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
As an example, suppose you are trying to find the commit that broke a
|
|
feature that was known to work in version `v2.6.13-rc2` of your
|
|
project. You start a bisect session as follows:
|
|
|
|
------------------------------------------------
|
|
$ git bisect start
|
|
$ git bisect bad # Current version is bad
|
|
$ git bisect good v2.6.13-rc2 # v2.6.13-rc2 is known to be good
|
|
------------------------------------------------
|
|
|
|
Once you have specified at least one bad and one good commit, `git
|
|
bisect` selects a commit in the middle of that range of history,
|
|
checks it out, and outputs something similar to the following:
|
|
|
|
------------------------------------------------
|
|
Bisecting: 675 revisions left to test after this (roughly 10 steps)
|
|
------------------------------------------------
|
|
|
|
You should now compile the checked-out version and test it. If that
|
|
version works correctly, type
|
|
|
|
------------------------------------------------
|
|
$ git bisect good
|
|
------------------------------------------------
|
|
|
|
If that version is broken, type
|
|
|
|
------------------------------------------------
|
|
$ git bisect bad
|
|
------------------------------------------------
|
|
|
|
Then `git bisect` will respond with something like
|
|
|
|
------------------------------------------------
|
|
Bisecting: 337 revisions left to test after this (roughly 9 steps)
|
|
------------------------------------------------
|
|
|
|
Keep repeating the process: compile the tree, test it, and depending
|
|
on whether it is good or bad run `git bisect good` or `git bisect bad`
|
|
to ask for the next commit that needs testing.
|
|
|
|
Eventually there will be no more revisions left to inspect, and the
|
|
command will print out a description of the first bad commit. The
|
|
reference `refs/bisect/bad` will be left pointing at that commit.
|
|
|
|
|
|
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 bisect/bad` will check out the first
|
|
bad revision, while `git bisect reset HEAD` will leave you on the
|
|
current bisection commit and avoid switching commits at all.
|
|
|
|
|
|
Alternate terms
|
|
~~~~~~~~~~~~~~~
|
|
|
|
Sometimes you are not looking for the commit that introduced a
|
|
breakage, but rather for a commit that caused a change between some
|
|
other "old" state and "new" state. For example, you might be looking
|
|
for the commit that introduced a particular fix. Or you might be
|
|
looking for the first commit in which the source-code filenames were
|
|
finally all converted to your company's naming standard. Or whatever.
|
|
|
|
In such cases it can be very confusing to use the terms "good" and
|
|
"bad" to refer to "the state before the change" and "the state after
|
|
the change". So instead, you can use the terms "old" and "new",
|
|
respectively, in place of "good" and "bad". (But note that you cannot
|
|
mix "good" and "bad" with "old" and "new" in a single session.)
|
|
|
|
In this more general usage, you provide `git bisect` with a "new"
|
|
commit that has some property and an "old" commit that doesn't have that
|
|
property. Each time `git bisect` checks out a commit, you test if that
|
|
commit has the property. If it does, mark the commit as "new";
|
|
otherwise, mark it as "old". When the bisection is done, `git bisect`
|
|
will report which commit introduced the property.
|
|
|
|
To use "old" and "new" instead of "good" and bad, you must run `git
|
|
bisect start` without commits as argument and then run the following
|
|
commands to add the commits:
|
|
|
|
------------------------------------------------
|
|
git bisect old [<rev>]
|
|
------------------------------------------------
|
|
|
|
to indicate that a commit was before the sought change, or
|
|
|
|
------------------------------------------------
|
|
git bisect new [<rev>...]
|
|
------------------------------------------------
|
|
|
|
to indicate that it was after.
|
|
|
|
To get a reminder of the currently used terms, use
|
|
|
|
------------------------------------------------
|
|
git bisect terms
|
|
------------------------------------------------
|
|
|
|
You can get just the old (respectively new) term with `git bisect terms
|
|
--term-old` or `git bisect terms --term-good`.
|
|
|
|
If you would like to use your own terms instead of "bad"/"good" or
|
|
"new"/"old", you can choose any names you like (except existing bisect
|
|
subcommands like `reset`, `start`, ...) by starting the
|
|
bisection using
|
|
|
|
------------------------------------------------
|
|
git bisect start --term-old <term-old> --term-new <term-new>
|
|
------------------------------------------------
|
|
|
|
For example, if you are looking for a commit that introduced a
|
|
performance regression, you might use
|
|
|
|
------------------------------------------------
|
|
git bisect start --term-old fast --term-new slow
|
|
------------------------------------------------
|
|
|
|
Or if you are looking for the commit that fixed a bug, you might use
|
|
|
|
------------------------------------------------
|
|
git bisect start --term-new fixed --term-old broken
|
|
------------------------------------------------
|
|
|
|
Then, use `git bisect <term-old>` and `git bisect <term-new>` instead
|
|
of `git bisect good` and `git bisect bad` to mark commits.
|
|
|
|
Bisect visualize/view
|
|
~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
To see the currently remaining suspects in 'gitk', issue the following
|
|
command during the bisection process (the subcommand `view` can be used
|
|
as an alternative to `visualize`):
|
|
|
|
------------
|
|
$ git bisect 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 visualize --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 suggested
|
|
revision is not a good one to test (e.g. it fails to build and you
|
|
know that the failure does not have anything to do with the bug you
|
|
are chasing), you can manually select a nearby commit and test that
|
|
one instead.
|
|
|
|
For example:
|
|
|
|
------------
|
|
$ git bisect good/bad # previous round was good or bad.
|
|
Bisecting: 337 revisions left to test after this (roughly 9 steps)
|
|
$ 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 a nearby commit by yourself, you can ask Git to do
|
|
it for you by issuing the command:
|
|
|
|
------------
|
|
$ git bisect skip # Current version cannot be tested
|
|
------------
|
|
|
|
However, if you skip a commit adjacent to the one you are looking for,
|
|
Git will be unable to tell exactly which of those commits was the
|
|
first bad one.
|
|
|
|
You can also skip a range of commits, instead of just one commit,
|
|
using range 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` and
|
|
`v2.6` (inclusive) 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/old, and exit with a
|
|
code between 1 and 127 (inclusive), except 125, if the current source
|
|
code is bad/new.
|
|
|
|
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.
|
|
|
|
--first-parent::
|
|
+
|
|
Follow only the first parent commit upon seeing a merge commit.
|
|
+
|
|
In detecting regressions introduced through the merging of a branch, the merge
|
|
commit will be identified as introduction of the bug and its ancestors will be
|
|
ignored.
|
|
+
|
|
This option is particularly useful in avoiding false positives when a merged
|
|
branch contained broken or non-buildable commits, but the merge itself was OK.
|
|
|
|
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
|
|
$ git bisect reset # quit the bisect session
|
|
------------
|
|
|
|
* 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
|
|
$ git bisect reset # quit the bisect session
|
|
------------
|
|
|
|
* 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
|
|
$ git bisect reset # quit the bisect session
|
|
------------
|
|
+
|
|
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 --no-ff 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"
|
|
$ git bisect reset # quit the bisect session
|
|
------------
|
|
+
|
|
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'
|
|
|
|
$ git bisect reset # quit the bisect session
|
|
------------
|
|
+
|
|
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'.
|
|
|
|
* Look for a fix instead of a regression in the code
|
|
+
|
|
------------
|
|
$ git bisect start
|
|
$ git bisect new HEAD # current commit is marked as new
|
|
$ git bisect old HEAD~10 # the tenth commit from now is marked as old
|
|
------------
|
|
+
|
|
or:
|
|
------------
|
|
$ git bisect start --term-old broken --term-new fixed
|
|
$ git bisect fixed
|
|
$ git bisect broken HEAD~10
|
|
------------
|
|
|
|
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.
|
|
|
|
SEE ALSO
|
|
--------
|
|
link:git-bisect-lk2009.html[Fighting regressions with git bisect],
|
|
linkgit:git-blame[1].
|
|
|
|
GIT
|
|
---
|
|
Part of the linkgit:git[1] suite
|