[PATCH 0/2] midx-write.c: do not optimize out writes with corrupt MIDXs

These two patches came from my work on implementing incremental MIDX layer compaction.

When rebasing on top of current 'master' (at the time of writing, 8745eae506f (The 17th batch, 2026-01-11)), I noticed an early 'test_done' in t5319 added by 6ce9d558ced (midx-write: skip rewriting MIDX with `--stdin-packs` unless needed, 2025-12-10). The series is structured as follows:

 - The first patch removes the extraneous 'test_done', which exposes a
   failing test which is marked as such.

 - The second patch explains and fixes the bug, un-marking the test
   as test_expect_failure.

I was originally planning on adding these onto my series under tb/incremental-midx-part-3.2. But I opted to split these patches out into their own topic to ensure they are picked up before v2.53.0 is tagged, should the larger series not be ready by then.

Thanks in advance for your review!

Taylor Blau (2):
  t/t5319-multi-pack-index.sh: drop early 'test_done'
  midx-write.c: assume checksum-invalid MIDXs require an update

 midx-write.c                | 14 ++++++++++++++
 t/t5319-multi-pack-index.sh |  2 --
 2 files changed, 14 insertions(+), 2 deletions(-)

base-commit: 8745eae506f700657882b9e32b2aa00f234a6fb6