[PATCH 0/3] object-file: fix ".keep" lockfile ownership in ODB transactions

[Justin Tobler <jltobler@gmail.com>]

Greetings,

This series addresses a bug report[1] regarding a git-receive-pack(1)
process deleting ".keep" lockfiles of with the same name but from
another concurrent git-receive-pack(1) process receiving an identical
packfile. Deleting the ".keep" lockfile for another process leaves its
newly written packfile vulnerable to deletion by another concurrent
housekeeping process.

The root of the problem here is that the temporary ".keep" lockfiles are
generated and registered in the object quarantine prior to being written
in the primary ODB. This means that even if the ODB transaction never
commits and exits early, the tempfile atexit(3) handler still runs and
tries to delete the lockfile at its expected final location. This
blindly deletes any file matching regardless of whether is was created
by the process.

The first two patches are some preparatory changes so that
`odb_transaction_files_write_pack()` is able to start explicitly
creating the lockfiles without relying on git-index-pack(1). Patch three
migrates lockfile generation to happen during ODB transaction commit to
ensure the lockfile is actually able to be written before registering it
as a tempfile.

Thanks,
-Justin

[1]: <932e8e425aecfbd33c1e5caf66c80a0226abacba.1789385483.git.gitgitgadget@gmail.com>

Justin Tobler (3):
  pack-write: lift and expose index-pack report parsing
  object-file: explicitly write ".keep" lockfile
  object-file: write ".keep" lockfiles during transaction commit

 object-file.c              | 117 +++++++++++++++++++++++++++++--------
 pack-write.c               |  69 ++++++++++++++++------
 pack.h                     |  10 ++++
 t/t5547-push-quarantine.sh |  29 ++++++++-
 4 files changed, 181 insertions(+), 44 deletions(-)


base-commit: f57c9a73884400380bddd172acc88b569834f909
-- 
2.55.0.424.g13c7afec21