Repositories created by newer version of git not supported (`reftable` ref format).

[yshui]

Describe the bug

error:
       … while fetching the input 'git+file:///tmp/repo'

       error: opening Git repository "/tmp/repo": unsupported extension name extensions.refstorage

I can't find anything in git's release notes indicating reftable has become the default, but for some reason all my new git repos start to use reftable.

Steps To Reproduce

Clone a flake repo (to explicitly choose ref format, use git clone --ref-format=reftable), run nix build.

Expected behavior

Builds

Metadata

nix-env (Nix) 2.31.2

Additional context

Checklist

• checked latest Nix manual (source)
• checked open bug issues and pull requests for possible duplicates

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[roberth]

• Blocked on Reftables support libgit2/libgit2#7117

Looks like we need to help them out.

[edolstra]

We should probably pass --ref-format=files when calling git fetch.

[roberth]

We don't control that for local user repositories though.

[edolstra]

Can't do much about those.