Julia EvansMay 16, 2024

in git, what ways are there to "lose" a commit in a way that you CAN'T recover using the reflog (so that you need to iterate over every single commit in the repository if you want to find it?

The only ways I know (using git's normal tools) are:

* using `git stash drop` or `git stash pop` to drop a stashed commit
* waiting 90+ days to try to recover the commit (so that it expires from the reflog)
* explicitly deleting the reflog in some way (rm -rf .git, git reflog expire, etc)

Show threadJulia EvansMay 16, 2024

also: have you even run into a situation where git *completely deleted* a commit that you needed? (where it wasn't recoverable with the reflog or with `git fsck`)

only interested in things that have *actually happened to you*, not "this could theoretically happen if…”

I'm trying to think about whether there's any normal way for that to happen except if you completely delete your git repository.

Show thread🌈 Andrew ☄️May 16, 2024
@b0rk if it was detached, or you have certain branch configs, then I think git gc can do it. I think similar commands can be configured to run automatically when your repo is large or slow.
Show threadJulia Evans
@bnut has that ever happened to you? i'm very aware of git gc but what I'm curious about is whether anyone has ever had a commit deleted by git gc that they cared about
May 16, 2024 at 7:51pmWeb
Show thread🌈 Andrew ☄️May 16, 2024
@b0rk I think I’ve had detached commits lost due to the automatic cleanup because it was a large repo. Although it was a long time ago, and I don’t remember the exact diagnosis sorry.
Show thread🌈 Andrew ☄️May 16, 2024
@b0rk Yeah, I’m fairly sure it was git prune as part of automatic gc due to a large slow repo. This thing: “Auto packing the repository for optimum performance […]".
Show thread🌈 Andrew ☄️May 16, 2024
@b0rk It was a commit I cared about, which I detached through an explicit mistake (like reset), but I pruned it due to a much more unexpected implicit mistake. I believe it was pruned when fetching to see if the lost commit had been pushed.
Show threadJulia EvansMay 17, 2024
@bnut thank you!
Show threadDrew 🐘May 17, 2024
@b0rk @bnut when I first started out with git in about 2007 or 2008 I really didn't understand the detached head state. I wasn't using any shell prompt integration and regularly made detached commits that I later needed to create a branch in order to retain. I'm not sure if the reflog existed back then but if it did I didn't know about it. As a result of that and a _really_ unhelpful git gc setting I blindly copied off SO I did lose some of those commits. Not really git's fault IMO.
Show threadDrew 🐘May 17, 2024
@b0rk @bnut The worst part about that whole episode was that git gc would regularly tell me it cleaned up a lot of garbage and the disk usage really went down so I thought I was doing something really good by running git gc after every checkout (or maybe it was every pull, long time ago). Little did I know I was happily just deleting my work.