Re: [PATCH 5/7] tmp-objdir: new API for creating and removing primary object dirs

Neeraj Singh [off-list ref] writes:

Is there state we care about besides objects and refs? Maybe we need to
introduce a transactional system for the entire repository like we have
for the refs-db.  In-process code that cares about oids that might be
only transactionally present can register a callback for when the transaction
commits or rollsback.  I'm not volunteering to write this, btw :).

I take it to mean by "objects and refs" that we care only about
objects that are reachable from the refs?  The index (the primary
index array plus extensions that record object names) also has
anchoring points we care about (ask "git fsck" what they are).

We can make the tmp object directory stuff more prevalent by using it in
git-apply and the merge stategy, and by using bulk-checkin while writing out
the cached tree and commits. This should flush out any issues and keep other
parts of the codebase honest.

I wonder what's so wrong about cruft objects in the main object
store that may be gc-ed away laster, though.  IOW, I wonder if it is
simpler to treat the quarantine while accepting dubious foreign data
via "git push" in receive-pack as an exception, not a norm.