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diff --git a/Documentation/git-bisect.txt b/Documentation/git-bisect.txt new file mode 100644 index 0000000000..1072fb87d1 --- /dev/null +++ b/Documentation/git-bisect.txt @@ -0,0 +1,202 @@ +git-bisect(1) +============= + +NAME +---- +git-bisect - Find the change that introduced a bug by binary search + + +SYNOPSIS +-------- +'git bisect' <subcommand> <options> + +DESCRIPTION +----------- +The command takes various subcommands, and different options depending +on the subcommand: + + git bisect start [<bad> [<good>...]] [--] [<paths>...] + git bisect bad <rev> + git bisect good <rev> + git bisect reset [<branch>] + git bisect visualize + git bisect replay <logfile> + git bisect log + git bisect run <cmd>... + +This command uses 'git-rev-list --bisect' option to help drive the +binary search process to find which change introduced a bug, given an +old "good" commit object name and a later "bad" commit object name. + +Basic bisect commands: start, bad, good +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The way you use it is: + +------------------------------------------------ +$ git bisect start +$ git bisect bad # Current version is bad +$ git bisect good v2.6.13-rc2 # v2.6.13-rc2 was the last version + # tested that was good +------------------------------------------------ + +When you give at least one bad and one good versions, it will bisect +the revision tree and say something like: + +------------------------------------------------ +Bisecting: 675 revisions left to test after this +------------------------------------------------ + +and check out the state in the middle. Now, compile that kernel, and +boot it. Now, let's say that this booted kernel works fine, then just +do + +------------------------------------------------ +$ git bisect good # this one is good +------------------------------------------------ + +which will now say + +------------------------------------------------ +Bisecting: 337 revisions left to test after this +------------------------------------------------ + +and you continue along, compiling that one, testing it, and depending +on whether it is good or bad, you say "git bisect good" or "git bisect +bad", and ask for the next bisection. + +Until you have no more left, and you'll have been left with the first +bad kernel rev in "refs/bisect/bad". + +Bisect reset +~~~~~~~~~~~~ + +Oh, and then after you want to reset to the original head, do a + +------------------------------------------------ +$ git bisect reset +------------------------------------------------ + +to get back to the master branch, instead of being in one of the +bisection branches ("git bisect start" will do that for you too, +actually: it will reset the bisection state, and before it does that +it checks that you're not using some old bisection branch). + +Bisect visualize +~~~~~~~~~~~~~~~~ + +During the bisection process, you can say + +------------ +$ git bisect visualize +------------ + +to see the currently remaining suspects in `gitk`. + +Bisect log and bisect replay +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The good/bad input is logged, and + +------------ +$ git bisect log +------------ + +shows what you have done so far. You can truncate its output somewhere +and save it in a file, and run + +------------ +$ git bisect replay that-file +------------ + +if you find later you made a mistake telling good/bad about a +revision. + +Avoiding to test a commit +~~~~~~~~~~~~~~~~~~~~~~~~~ + +If in a middle of bisect session, you know what the bisect suggested +to try next is not a good one to test (e.g. the change the commit +introduces is known not to work in your environment and you know it +does not have anything to do with the bug you are chasing), you may +want to find a near-by commit and try that instead. + +It goes something like this: + +------------ +$ git bisect good/bad # previous round was good/bad. +Bisecting: 337 revisions left to test after this +$ git bisect visualize # oops, that is uninteresting. +$ git reset --hard HEAD~3 # try 3 revs before what + # was suggested +------------ + +Then compile and test the one you chose to try. After that, tell +bisect what the result was as usual. + +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 giving +paths parameters when you say `bisect start`, like this: + +------------ +$ git bisect start -- arch/i386 include/asm-i386 +------------ + +If you know beforehand more than one good commits, you can narrow the +bisect space down without doing the whole tree checkout every time you +give good commits. You give the bad revision immediately after `start` +and then you give all the good revisions you have: + +------------ +$ 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 automatically bisect using: + +------------ +$ git bisect run my_script +------------ + +Note that the "run" script (`my_script` in the above example) should +exit with code 0 in case the current source code is good and with a +code between 1 and 127 (included) in case the current source code is +bad. + +Any other exit code will abort the automatic bisect process. (A +program that does "exit(-1)" leaves $? = 255, see exit(3) manual page, +the value is chopped with "& 0377".) + +You may often find that during bisect you want to have near-constant +tweaks (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 other 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, with the "run" script, you can apply that tweak +before compiling, run the real test, and after the test decides if the +revision (possibly with the needed tweaks) passed the test, rewind the +tree to the pristine state. Finally the "run" script can exit with +the status of the real test to let "git bisect run" command loop to +know the outcome. + +Author +------ +Written by Linus Torvalds <torvalds@osdl.org> + +Documentation +------------- +Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>. + +GIT +--- +Part of the gitlink:git[7] suite |