X-Git-Url: https://git.tokkee.org/?a=blobdiff_plain;f=Documentation%2Fgit-bisect.txt;h=ab60a1847042a8ef28e019c8ad1a620ef5fd41d7;hb=b35acb53458d0f99ba2400b902980b35e5acc2d3;hp=c39d957c3a3a432f5e685d44066c145f03b96365;hpb=71ee7fd15457a0252c089420b5b66de266dcbd2f;p=git.git

diff --git a/Documentation/git-bisect.txt b/Documentation/git-bisect.txt
index c39d957c3..ab60a1847 100644
--- a/Documentation/git-bisect.txt
+++ b/Documentation/git-bisect.txt
@@ -8,6 +8,7 @@ git-bisect - Find by binary search the change that introduced a bug
 
 SYNOPSIS
 --------
+[verse]
 'git bisect' <subcommand> <options>
 
 DESCRIPTION
@@ -241,7 +242,12 @@ 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).
+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
@@ -274,61 +280,68 @@ $ 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 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.
-
-Author
-------
-Written by Linus Torvalds <torvalds@osdl.org>
-
-Documentation
--------------
-Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>.
+This shows that you can do without a run script if you write the test
+on a single line.
 
 SEE ALSO
 --------