SYNOPSIS
--------
+[verse]
'git bisect' <subcommand> <options>
DESCRIPTION
on the subcommand:
git bisect help
- git bisect start [<bad> [<good>...]] [--] [<paths>...]
+ git bisect start [
--no-checkout] [<bad> [<good>...]] [--] [<paths>...]
git bisect bad [<rev>]
git bisect good [<rev>...]
git bisect skip [(<rev>|<range>)...]
- git bisect reset [<branch>]
+ git bisect reset [<commit>]
git bisect visualize
git bisect replay <logfile>
git bisect log
Bisect reset
~~~~~~~~~~~~
-To return to the original head after a bisect session, issue the
-following command:
+After a bisect session, to clean up the bisection state and return to
+the original HEAD, issue the following command:
------------------------------------------------
$ git bisect reset
------------------------------------------------
-This resets the tree to the original branch instead of being on the
-bisection commit ("git bisect start" will also do that, as it resets
-the bisection state).
+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
~~~~~~~~~~~~~~~~
$ git bisect skip # Current version cannot be tested
------------
-But computing the commit to test may be slower afterwards and git may
-eventually not be able to tell the first bad commit among a bad commit
-and one or more skipped commits.
+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:
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).
+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
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
--------
$ git bisect run make test # "make test" builds and tests
------------
-* Automatically bisect a broken test suite:
+* Automatically bisect a broken test case:
+
------------
$ cat ~/test.sh
#!/bin/sh
-make || exit 125 # this skips broken builds
-make test # "make test" runs the test suite
-$ git bisect start v1.3 v1.1 -- # v1.3 is bad, v1.1 is good
+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 to use a custom script outside the repository to prevent
-interactions between the bisect, make and test processes and the
-script.
-+
-"make test" should "exit 0", if the test suite 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 a broken test case:
+* Automatically bisect with temporary modifications (hot-fix):
+
------------
$ cat ~/test.sh
#!/bin/sh
-make || exit 125 # this skips broken builds
-~/check_test_case.sh # does the test case passes ?
-$ git bisect start HEAD HEAD~10 -- # culprit is among the last 10
-$ git bisect run ~/test.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
------------
+
-Here "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" scripts are
-outside the repository to prevent interactions between the bisect,
-make and test processes and the scripts.
+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 suite:
+* 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"
------------
+
-Does the same as the previous example, but on a single line.
+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'.
-Author
-------
-Written by Linus Torvalds <torvalds@osdl.org>
-Documentation
--------------
-Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>.
+SEE ALSO
+--------
+link:git-bisect-lk2009.html[Fighting regressions with git bisect],
+linkgit:git-blame[1].
GIT
---