Read alternate object stores when opening a repository#194
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go-git's PlainOpen chroots its billy filesystem to .git, so absolute paths in objects/info/alternates can't be followed and borrowed objects are invisible. Repos created with clone --shared or --reference would fail to resolve any SHA in the borrowed history with "reference not found". Reopen the storage with AlternatesFS rooted at the volume root so go-git can follow alternates. PlainOpenOptions doesn't expose this so the storage has to be rebuilt by hand after discovery. Reported in #166.
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go-git's
PlainOpenchroots its billy filesystem to.git, so absolute paths inobjects/info/alternatescan't be followed and borrowed objects are invisible. In a repo created withgit clone --sharedor--reference, any SHA in the borrowed history fails withreference not foundwhile HEAD (a local object) works. That matches the report in #166.PlainOpenOptionsdoesn't exposeAlternatesFS, so after discovery we rebuild the storage withfilesystem.Options{AlternatesFS: osfs.New(<volume root>)}and reopen. If the storer isn't a*filesystem.Storageor the reopen fails we keep the original repo, so this is strictly additive.Abbreviated SHAs that live only in the alternate still fail because go-git's
resolveHashPrefixdoesn't traverse alternates; #193 covers that via thegit rev-parsefallback. The two together handle everything in the #166 report.The repro matrix that pinned this down is at
/tmp/repro-resolvelocally if anyone wants it; not committing it since it's a throwaway.