Description

alynn-coefficient

opened on Mar 19, 2026

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On git repositories using the new reftable format (slated to become the default in the upcoming Git 3.0.0), GitPython detects the wrong ref as being active.

Observe, with the traditional "files" format:

mkdir test
cd test
git init --ref-format=files
uvx --with gitpython python -c "import git; print(git.Repo('.').active_branch.name)"

Produces main as expected. However:

mkdir test
cd test
git init --ref-format=reftable
uvx --with gitpython python -c "import git; print(git.Repo('.').active_branch.name)"

Produces .invalid.

Activity

1. Byron

   added

   acknowledged

   help wanted

   on Mar 19, 2026
2. Byron commented on Mar 19, 2026

   

   Byron

   on Mar 19, 2026

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   While the object database with SHA256 should be fine, the reference handling will have a problem as it's currently done in pure python.

   To support this properly, I think it would have to detect reftables and switch to an alternative implementation, probably one that just uses Git under the hood.
3. alynn-coefficient commented on Mar 20, 2026

   

   alynn-coefficient

   on Mar 20, 2026

   Author

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   Is there a shorter-term option perhaps to add the detection and just error loudly? I realise that full native reftables support may be a longer-term project.

   Reacted by Sebastian Thiel
4. Byron

   linked a pull request that will close this issueFix `Repo.active_branch` resolution for reftable-backed repositories #2114on Mar 21, 2026
5. Byron

   closed this as completedin #2114on Mar 21, 2026
6. planetmarshall commented on Apr 1, 2026

   

   planetmarshall

   on Apr 1, 2026

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   On git repositories using the new reftable format (slated to become the default in the upcoming Git 3.0.0)...

   Also worth noting that reftables may already be widely used on macos where a case-insensitive filesystem is the default - due to git suggesting that users migrate if it detects a case-sensitivity conflict:

   error: You're on a case-insensitive filesystem, and the remote you are
   trying to fetch from has references that only differ in casing. It
   is impossible to store such references with the 'files' backend. You
   can either accept this as-is, in which case you won't be able to
   store all remote references on disk. Or you can alternatively
   migrate your repository to use the 'reftable' backend with the
   following command:
   
       git refs migrate --ref-format=reftable
   
   Please keep in mind that not all implementations of Git support this
   new format yet. So if you use tools other than Git to access this
   repository it may not be an option to migrate to reftables.
   

   Was caught by this recently when using repo.index.diff("HEAD") to detect a changeset.

   Reacted by Sebastian Thiel

   Reacted by Eliah Kagan

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