Re: git gc error with git 2.37.2? (Introduced in 5a5ea141e7)

From: Jeff King <peff@peff.net>
Date: Oct 17, 2022, 17:42 UTC
Message-ID: <Y02T9ssqqwX3mfRj@coredump.intra.peff.net>
In-Reply-To: <2C46C994-6023-4C69-92DF-73291A6AF94D@gmail.com>

On Mon, Oct 17, 2022 at 07:10:44PM +0200, Paul Wagland wrote:

Show 17 quoted lines

> On git-users, I started a discussion(*) about a git gc error that I was getting that started with git 2.37.2. After some followup from Mathias on that list, I have determined that the issues that I a having started with the following commit:  https://github.com/git/git/commit/5a5ea141e7 ("revision: mark blobs needed for resolve-undo as reachable", 2022-06-09)
> 
> When I compile git locally with:
>    git checkout dc8c8deaa6
>    make
>    git rev-list --objects --indexed-objects
> 
> Then it works.
> 
>    git checkout 5a5ea141e7
>    make
>    git rev-list --objects --indexed-objects
> 
> Then I get the error:
>    fatal: missing blob object ‘1d0f34d1c4314efcff527847755e4ccc77d44fb6'
> 
> How can I further diagnose how to fix this?

It sounds like there's a resolve-undo extension in your index that references that blob, but the blob was removed from the repository (probably by a gc prior to 5a5ea141e7, which was trying to prevent this corruption).

I'd expect that the resolve-undo extension would eventually be dropped once a merge is finished, but I'm not very familiar with that code. Is the repository in question mid-merge, or does it happen all the time?

If there are no changes you need to keep in the index or working tree, I expect that a workaround would be:

  rm -f .git/index
  git reset
  git update-index --refresh

to rewrite the index from scratch. Then the problem should not recur, as you'd be using a version with 5a5ea141e7 from here on out.

-Peff