Driving Git Bisect: Manual and Automatic Methods

"git log -S<string>"). Driving a bisection manually ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ At this point there are basically 2 ways to drive the search. It can be driven manually by the user or it can be driven automatically by a script or a command. If the user is driving it, then at each step of the search, the user will have to test the current commit and say if it is "good" or "bad" using the "git bisect good" or "git bisect bad" commands respectively that have been described above. For example: ------------- $ git bisect bad Bisecting: 5480 revisions left to test after this (roughly 13 steps) [66c0b394f08fd89236515c1c84485ea712a157be] KVM: kill file->f_count abuse in kvm ------------- And after a few more steps like that, "git bisect" will eventually find a first bad commit: ------------- $ git bisect bad 2ddcca36c8bcfa251724fe342c8327451988be0d is the first bad commit commit 2ddcca36c8bcfa251724fe342c8327451988be0d Author: Linus Torvalds <torvalds@linux-foundation.org> Date: Sat May 3 11:59:44 2008 -0700 Linux 2.6.26-rc1 :100644 100644 5cf82581... 4492984e... M Makefile ------------- At this point we can see what the commit does, check it out (if it's not already checked out) or tinker with it, for example: ------------- $ git show HEAD commit 2ddcca36c8bcfa251724fe342c8327451988be0d Author: Linus Torvalds <torvalds@linux-foundation.org> Date: Sat May 3 11:59:44 2008 -0700 Linux 2.6.26-rc1 diff --git a/Makefile b/Makefile index 5cf8258..4492984 100644 --- a/Makefile +++ b/Makefile @@ -1,7 +1,7 @@ VERSION = 2 PATCHLEVEL = 6 -SUBLEVEL = 25 -EXTRAVERSION = +SUBLEVEL = 26 +EXTRAVERSION = -rc1 NAME = Funky Weasel is Jiggy wit it # *DOCUMENTATION* ------------- And when we are finished we can use "git bisect reset" to go back to the branch we were in before we started bisecting: ------------- $ git bisect reset Checking out files: 100% (21549/21549), done. Previous HEAD position was 2ddcca3... Linux 2.6.26-rc1 Switched to branch 'master' ------------- Driving a bisection automatically ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The other way to drive the bisection process is to tell "git bisect" to launch a script or command at each bisection step to know if the current commit is "good" or "bad". To do that, we use the "git bisect run" command. For example: ------------- $ git bisect start v2.6.27 v2.6.25 Bisecting: 10928 revisions left to test after this (roughly 14 steps) [2ec65f8b89ea003c27ff7723525a2ee335a2b393] x86: clean up using max_low_pfn on 32-bit $ $ git bisect run grep '^SUBLEVEL = 25' Makefile running grep ^SUBLEVEL = 25 Makefile Bisecting: 5480 revisions left to test after this (roughly 13 steps) [66c0b394f08fd89236515c1c84485ea712a157be] KVM: kill file->f_count abuse in kvm running grep ^SUBLEVEL = 25 Makefile SUBLEVEL = 25 Bisecting: 2740 revisions left to test after this (roughly 12 steps) [671294719628f1671faefd4882764886f8ad08cb] V4L/DVB(7879): Adding cx18 Support for mxl5005s ... ... running grep ^SUBLEVEL = 25 Makefile Bisecting: 0 revisions left to test after this (roughly 0 steps) [2ddcca36c8bcfa251724fe342c8327451988be0d] Linux 2.6.26-rc1 running grep ^SUBLEVEL = 25 Makefile 2ddcca36c8bcfa251724fe342c8327451988be0d is the first bad commit commit 2ddcca36c8bcfa251724fe342c8327451988be0d Author: Linus Torvalds <torvalds@linux-foundation.org> Date: Sat May 3 11:59:44 2008 -0700 Linux 2.6.26-rc1 :100644 100644 5cf82581... 4492984e... M Makefile bisect run success ------------- In this example, we passed "grep '^SUBLEVEL = 25' Makefile" as parameter to "git bisect run". This means that at each step, the grep command we passed will be launched. And if it exits with code 0 (that means success) then git bisect will mark the current state as "good". If it exits with code 1 (or any code between 1 and 127 included, except the special code 125), then the current state will be marked as "bad". Exit code between 128 and 255 are special to "git bisect run". They make it stop immediately

This text explains the two ways to drive the Git bisect process: manually, where the user tests each commit and marks it as 'good' or 'bad', and automatically, using the 'git bisect run' command with a script or command to determine the status of each commit, with examples of both methods and their usage.