This does two things:
- Pass commit oids instead of `Gitlab::Git::Commit`s. We only need the
former.
- Depend on only the target repository for conflict listing. For
conflict resolution, treat one repository as a remote one so that we can
implement it as such in Gitaly.
I don't know why this happens exactly, but given an upstream and fork repository
from a customer, both of which required GC, resolving conflicts would corrupt
the fork so badly that it couldn't be cloned.
This isn't a perfect fix for that case, because the MR may still need to be
merged manually, but it does ensure that the repository is at least usable.
My best guess is that when we generate the index for the conflict
resolution (which we previously did in the target project), we obtain a
reference to an OID that doesn't exist in the source, even though we already
fetch the refs from the target into the source.
Explicitly setting the source project as the place to get the merge index from
seems to prevent repository corruption in this way.
GitLab Bot