Backport #31790 by @wolfogre
Fix#31271.
When gogit is enabled, `IsObjectExist` calls
`repo.gogitRepo.ResolveRevision`, which is not correct. It's for
checking references not objects, it could work with commit hash since
it's both a valid reference and a commit object, but it doesn't work
with blob objects.
So it causes #31271 because it reports that all blob objects do not
exist.
Co-authored-by: Jason Song <i@wolfogre.com>
(cherry picked from commit 144648a4afdd93d534875a86c50ec61c860878f3)
3e091b9bac