Stefan Beller [off-list ref] writes:
quoted
At the implementation level, it should have a
hashtable (lazily populated) for all the objects in a single
$GIT_OBJECT_DIRECTORY, grafts/replace info, and a set of pointers to
other object-store instances that are its alternate object stores.
So one repository has one or more object stores?
One repository foo/.git/ has one foo/.git/objects/ directory, so it
has its own single object store. That object store may refer to
another object store by having foo/.git/objects/info/alternates.
Similarly, foo/.git/objects/info/grafts and foo/.git/refs/replace/
would belong to the single object store repository foo/.git/ has.
I would expect that most of the time the question from above
"give me info on the object I can refer to with this object name"
is asked with the additional information: "and I know it is in this
repository", so we rather want to have
lookup_object(struct *repo, char *name);
instead of
lookup_object(struct *object_store, char *name);
Absolutely. That is why repository has its own single object_store,
which may refer to other object_stores.