- Notice a bug that you recall was working earlier. (but apparently there were no automated tests checking it)
- Task: find the change that broke it
- Find an old commit where it was still working.
- Binary search the commit since then to locate the breaking change.
Preferably write an automated test that can verify the feature. Put it in a separate test file in the workspace.
$ git checkout master $ git bisect start $ git bisect bad $ git checkout sha1-that-is-known-to-be-good $ git bisect good ...