[PATCH 0/3] refs: report old OIDs for batched deletions

[Maciej Ciemborowicz <maciej.ciemborowicz@gmail.com>]

This follows up on the reference-transaction bug report at [1].

The reference-transaction hook reports an all-zero update when `git branch
-d`, `git tag -d`, `git remote prune`, or `git fetch --prune` deletes a
ref. This prevents hook consumers from identifying the object that the ref
pointed to.

For branch and tag deletion, this is a regression caused by 8198907795 (use
delete_refs when deleting tags or branches, 2021-01-21). That change made
large deletions much faster by batching them, but the batch helper did not
accept the old OIDs that both callers had already resolved. The pruning paths
have the same omission.

Teach refs_delete_refs() to accept optional old OIDs, then pass the values
already available to the branch, tag, fetch, and remote callers. This keeps a
single batched transaction and does not add any ref reads.

Deleting 10,000 packed tags took a median of 0.86 seconds before this series
and 0.85 seconds after it across five runs, which is within measurement noise.

The regression tests use packed refs and cover the files and reftable
backends, distinct old OIDs, and regular and atomic fetch pruning. The full
test suite passes with DEVELOPER=1. Additional checks covered SHA-1, SHA-256,
broken and symbolic refs, and refs shadowed between loose and packed storage.

[1] https://lore.kernel.org/git/CACQ=SRGTTdQ+dHXhN6F52dBv5KxZBRfk_Em2fvmEmGJDoB6oTg@mail.gmail.com/

Maciej Ciemborowicz (3):
  refs: allow callers to supply old OIDs for batch deletion
  branch, tag: retain old OIDs in batched deletions
  fetch, remote: retain old OIDs when pruning refs

 bisect.c                         |  2 +-
 builtin/branch.c                 |  7 +++-
 builtin/fetch.c                  | 11 +++--
 builtin/remote.c                 | 33 ++++++++++++---
 builtin/tag.c                    |  7 +++-
 refs.c                           | 26 +++++++-----
 refs.h                           | 12 +++++-
 t/helper/test-ref-store.c        |  2 +-
 t/t1416-ref-transaction-hooks.sh | 70 ++++++++++++++++++++++++++++++++
 9 files changed, 144 insertions(+), 26 deletions(-)


base-commit: e9019fcafe0040228b8631c30f97ae1adb61bcdc
-- 
2.39.3 (Apple Git-146)