For those (like me) who were not aware of git bisect:

The git bisect command is a powerful tool that quickly checks out a commit halfway between a known good state and a known bad state and then asks you to identify the commit as either good or bad. Then it repeats until you find the exact commit where the code in question was first introduced.

Quite a few times, sure. git bisect is a specific case of a more general technique – binary search fault localization – which comes in handy every once in a while (you can go a long while without needing it, but when you do need it, you’ll be thankful for it). If you can’t otherwise trace where in the code something is going wrong, bisect the code: comment or remove half of it out, see if it reproduces (therefore localizing it to either the removed or the remaining half), and repeat. If you’re working with some software that’s breaking on your config after a major version bump, bisect your config. Don’t have an idea what introduced a bug into your branch? git bisect.

Yeah it’s saved my bacon a bunch of times

Just yesterday 😅 there’s a bug in the main branch of Lemmy itself that I was trying to pinpoint (introduced after 0.18.0 was tagged). Instead of walking through all recent commits manually, I used bisect. Bisect is not a magic bullet, and you could do the same manually, but it’s a good tool in the toolbox to know sometimes.

It’s mostly relevant for a project you’re not familiar with (perhaps it is/was someone else’s project, or perhaps a project that’s too large for a single user to be familiar with the entirety of), since it helps you figure out where a bug came from.

If you’re familiar with the entire project you usually don’t need it IME.

I certainly have! Although I can count on two hands how many times I’ve used it, it has proven to be extremely powerful when trying to pin-point changes that introduced non-trivial bugs. Specifically if the time-span of when the bug was introduced it is very useful to quickly sift through commit history.

Yes, many times. And I recall using the technique manually back when I was working with Subversion many, many years ago. No fun stories though, sorry, it’s just another tool in a toolbox.

Usually when theres a “mystery” bug on something that already worked before. Spending half a day running the build script over and over again, is still faster than debugging in different parts of the codebase with the hope of finding some hint.

No, but I once wrote my one git bisect without realizing git bisect existed.

I used it to track down a commit that caused an old bug. The commit didn’t pop out on a cursory check, and I was getting lost in tracking the test results.