Hi Jonathan,

git 2.56.0 was released upstream on September 28 and would be great to
see in unstable. One change in it is particularly important for CI
systems: object lookups now recover when a multi-pack-index names an
owning pack that a concurrent repack already deleted. Before 2.56,
that state makes git spuriously report objects as missing (cat-file,
rev-parse, fsck, fetch negotiation), and on a persistent mirror there
is no self-heal. We ran into exactly this in production.

Details:
- upstream merge:
https://github.com/git/git/commit/1137fddf4079a49c28b7735f4216e02737257cf0
- core commit:
https://github.com/git/git/commit/8f909ff4e9e883bf4938c0f0f67b9e1d48cc0167
- release notes:
https://github.com/git/git/blob/v2.56.0/Documentation/RelNotes/2.56.0.adoc
- a self-contained reproduction, failing on 2.55.0 and passing on
  2.56.0: https://github.com/felipecrs/git-stale-midx-repro

Heads-up that upstream enables Rust by default from 2.56, and the
2.55.0 packaging disabled it ("debian/rules: disable Rust for now"),
so packaging 2.56 may need a decision there.

Thanks for maintaining git!

Best regards,
Felipe Santos