Start tracking packfiles per object database source

Hi,

the struct packfile_store tracks packfiles we have in the repository so that we can look up objects stored therein. Right now, the packfile store is tracked on the object database level -- each object database has exactly one packfile store. Consequently, we track packfiles that are part of different object database sources via the same packfile store.

This patch series refactors this so that we instead have one packfile store per ODB source. This means that access to any object, regardless of whether it is stored in a packfile or in a loose object, is always done via its owning source.

This is the last step required for pluggable object databases: all object access is routed through sources, and we can thus now abstract these sources and then plug in a different implementation. Of course, these abstractions are still very leaky, and we still reach into the implementation details in a bunch of files. But this is something that will be addressed over subsequent steps.

Thanks!

Patrick

To: git@vger.kernel.org

--- b4-submit-tracking ---

This section is used internally by b4 prep for tracking purposes.

{ "series": { "revision": 1, "change-id": "20251201-b4-pks-pack-store-via-source-fd43dc0765a7", "prefixes": [] } }

Closes Move packfile-related state into `struct odb_so... (#547).