If you have a branch which always builds and tests green, you can add a new test, choose a red commit and a green commit and run `git bisect` in a loop to automatically get to the commit that caused the behaviour in that test to regress.
Did just that last week.. But for some reason, each time I share the result of a git bisect some thinks that I'm a wizard and instead of learning how to do it themselves they ask me later..
Thanks but its git bisect the magic tool not me (writing the shell script did take me some times though).
