[vegerot]

Problem

sl cannot open a Git repo that stores refs in the reftable format:

$ git init --ref-format=reftable repo && cd repo && sl status
abort: ... opening git store: unsupported extension name extensions.refstorage; class=Repository (6)

Git marks such a repo with extensions.refstorage = reftable. GitStore::open opens the repo with libgit2 1.9, which rejects any extension it does not know. Only libgit2 2.0, currently a release candidate, accepts refstorage.

Reading reftable refs already works since 5b7f339 ("gitcompat: support reftable references"). The failure happens before that code runs.

sl init --git and sl clone --git fail the same way when reftable is Git's default, for example with feature.experimental = true.

Solution

Register refstorage with libgit2 (git2::opts::set_extensions) before opening the repo. This is enough because GitStore uses libgit2 only for the object database, which does not depend on the ref format. Refs go through gitcompat, which runs git for reftable repos.

extensions.refstorage can also be <format>://<path>, which stores refs at a custom path. gitcompat cannot read those, and libgit2 no longer rejects them for us, so GitStore::open rejects them itself:

Git references stored at a custom path are not supported (extensions.refstorage = "reftable:///path/to/refs")

Before this change, that case failed with the generic unsupported extension name error.

Test plan

New test-dotgit-reftable.t: sl log reads a reftable repo, and git log shows a commit made by sl commit. Before this change it fails with the error above.

The test needs Git 2.45 or later, the first version with the reftable backend (git init --ref-format=reftable). With an older Git the test fails; it does not skip.

make oss on macOS with Git 2.56.0, then:

• run-tests.py --with-hg ../out/sl test-dotgit-*.t: 12 ran, 0 failed, 1 skipped (test-dotgit-gpg.t)
• By hand: sl init --git and sl clone --git work with reftable as Git's default.
• By hand: a repo with extensions.refstorage = reftable://<path> shows the new error, and git log is unchanged afterwards.

No test covers the custom path error.

Closes #1391

🤖 Generated with Claude Code

Co-Authored-By: Claude Fable 5.2 noreply@anthropic.com
Claude-Session: https://claude.ai/code/session_01ECQd3Jewp71mGty3KKcGs9

[meta-codesync]

This pull request has been imported. If you are a Meta employee, you can view this in D131048102. (Because this pull request was imported automatically, there will not be any future comments.)