Re: [BUG] reference-transaction reports zero OIDs for branch and tag deletion

From: Maciej Ciemborowicz <maciej.ciemborowicz@gmail.com>
Date: Sep 19, 2026, 15:42 UTC
Message-ID: <CACQ=SRHthWOLVXmY6wgknOPgpQ+oB1vV-Q0AL=mK9mXb2Xy9Nw@mail.gmail.com>
In-Reply-To: <CALnO6CBUr3=Cj57ikytiPxU-1hZkYu1Z3fRPydhFLqJHprbDew@mail.gmail.com>

Commit `6754159767` introduced `reference-transaction` in Git 2.28. In Git 2.28-2.30, `git branch -D` and `git tag -d` used `delete_ref()` with the known old OID. Commit `8198907795`, before Git 2.31, replaced single-ref deletion with `delete_refs()`. The new function preserved only the ref names and called:

```c ref_transaction_delete(transaction, refname, NULL, NULL, ...) ```

Without the old OID, the `REF_HAVE_OLD` flag is not set, so the hook receives:

```text 000000... 000000... refs/heads/topic ```

The change was intended to speed up deletion of 24,000 tags from roughly 30 minutes to 5 seconds. The loss of information exposed to the hook appears to have been a side effect. So I assume this is a bug introduced by that optimization, and it should be fixed in a way that preserves the performance improvement. That seems feasible.

Cheers, Maciej Ciemborowicz

On Sat, Sep 19, 2026 at 4:59 PM D. Ben Knoble <ben.knoble@gmail.com> wrote:

Show 20 quoted lines

>
> On Sat, Sep 19, 2026 at 9:34 AM Maciej Ciemborowicz
> <maciej.ciemborowicz@gmail.com> wrote:
> >
> > Since Git 2.31, the reference-transaction hook receives all-zero old and
> > new object IDs when a branch or tag is deleted with a high-level command.
>
> [snip]
>
> > Was this loss of information intentional? If not, could the previous
> > object ID be restored for these deletion paths? If it is intentional,
> > the documentation may need to clarify that high-level deletion commands
> > can provide a zero-to-zero record.
>
> Since you seem to have identified a "good" and "bad" version with a
> reproduction script, I suspect "git bisect" is a good way to answer
> your questions about intent.
>
> --
> D. Ben Knoble