Maciej Ciemborowicz reported that 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. His examples are git branch -d, git branch -D, git tag -d and deletion of a remote-tracking ref by git remote prune. Git 2.28 through 2.30 reported the previous object ID followed by the zero ID, so that information is now lost. He says the behaviour persists in Git 2.55 with both the files and reftable backends.
The thread has 54 messages and involves Karthik Nayak, Patrick Steinhardt, D. Ben Knoble and Junio Hamano. The excerpts do not show the technical conclusions of that discussion.
In the latest messages Junio Hamano noted that nobody had shown interest in the topic for a full month. He said that unless volunteers appear to review it in a few weeks, he will discard the topic from his tree, because 'seen' is crowded with topics collecting dust.
Ciemborowicz replied that he understood and hoped someone else might review it or provide a patch. As of now the regression has no fix queued.