A (Brief!) Intro to Git Bisect
Doug Price / @solipet
January 10, 2017
Git Bisect
Use binary search to find the commit
that introduced a change
Basic Usage
``` bash
$ git bisect start
$ git bisect bad
$ git checkout last-known-working-tag
$ git bisect good
```
Pick your own terms
If "good" and "bad" don't fit the search you are doing, use different terms.
``` bash
$ git bisect start --term-new foo --term-old bar
$ git bisect foo
$ git bisect bar last-known-bar-tag
```
Don't be so judgy!
If "good" and "bad" are too judgemental for you, pick terms you like.
``` bash
$ git bisect start --term-new a-for-effort --term-old solid
$ git bisect a-for-effort
$ git bisect solid last-known-solid-tag
```
Or perhaps you're looking for a regression in performance...
``` bash
$ git bisect start --term-new slow --term-old fast
$ git bisect slow
$ git bisect fast last-known-fast-tag
```
Or maybe you just noticed that things got way better and you want to know how/why/thanks to whom...
``` bash
$ git bisect start --term-new amazing --term-old meh
$ git bisect amazing
$ git bisect meh last-known-meh-tag
```
Oops! I meant good, not bad!
No problem! Just recode the bisect to a file, reset it, then edit the file and replay it!
``` bash
$ git bisect bad
$ git bisect log > bisect_log
# edit bisect_log to git rid of bad call
$ git bisect reset
$ git bisect replay bisect_log
```
Ugh! This commit is so f'd I can't even test it!!
No problem -- just skip it.
``` bash
$ git bisect skip
```
Or, if you know you're close to a commit that you can test, check it out!
``` bash
$ git bisect good/bad # previous round was good or bad.
Bisecting: 337 revisions left to test after this (roughly 9 steps)
$ git reset --hard HEAD~3 # try 3 revisions before what
# was suggested
$ git bisect good/bad
```
OK, that was fun the first time...
If your test can be automated with a script, then the entire bisect can be automated!
``` bash
$ git bisect run test_script.sh arguments
```
Let's give it a try!
References
https://git-scm.com/docs/git-bisect
(It's all right here! ^^^)