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
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:
+
------------
This shows that you can do without a run script if you write the test
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>.
-
SEE ALSO
--------
link:git-bisect-lk2009.html[Fighting regressions with git bisect],