[PATCH 0/3] refs: fix some bugs with batched-updates

In 23fc8e4f61 (refs: implement batch reference update support, 2025-04-08) we introduced a mechanism to batch reference updates. The idea being that we wanted to batch updates similar to a transaction, but allow certain updates to fail. This would help reference backends optimize such operations and also remove the overhead of processing updates individually. Especially for the reftable backend, where batching updates would ensure that the autocompaction would only occur at the end of the batch instead of after every reference update.

As of 9d2962a7c4 (receive-pack: use batched reference updates, 2025-05-19) we also updated the 'git-fetch(1)' and 'git-receive-pack(1)' command to use batched reference updates. This series fixes some bugs that we found at GitLab by running our Gitaly service with the `next` build of Git.

The first being in the files backend, which missed skipping over failed updates in certain flows. When certain individual updates fail, we mark them as such. However, we missed skipping over such failed updates, which can cause a SEGFAULT.

The other is in the git-receive-pack(1) implementation when a user pushes multiple branches such as:

  delete refs/heads/branch/conflict
  create refs/heads/branch

Before using batched updates, the references would be applied sequentially and hence no conflicts would arise. With batched updates, while the first update applies, the second fails due to F/D conflict. A similar issue was present in 'git-fetch(1)' and was fixed by using separating out reference pruning into a separate transaction. Apply a similar mechanism for 'git-receive-pack(1)' and separate out reference deletions into its own batch.

This is based off master 7014b55638 (A bit more topics for -rc1, 2025-05-30), with the changes from kn/fetch-push-bulk-ref-update merged in.

---
 builtin/receive-pack.c           | 23 +++++++++++++++++++----
 refs/files-backend.c             |  7 +++++++
 t/t1400-update-ref.sh            | 14 ++++++++++++++
 t/t1416-ref-transaction-hooks.sh |  2 ++
 t/t5516-fetch-push.sh            | 23 ++++++++++++++++-------
 5 files changed, 58 insertions(+), 11 deletions(-)

Karthik Nayak (3):
      refs/files: skip updates with errors in batched updates
      t5516: use double quotes for tests with variables
      receive-pack: handle reference deletions separately

base-commit: 931c39f05e078e0df968a439379cb04b5c4666ef change-id: 20250528-6769-address-test-failures-in-the-next-branch-caused-by-batched-reference-updates-24ff53680144

Thanks
- Karthik