The object ID to expand
The length of the object ID (in nibbles, or packets of 4 bits; the number of hex characters)
The (optional) type of the object to search for; leave as 0 or set to git_object_t.GIT_OBJECT_ANY to query for any object matching the ID.
The information about object IDs to query in git_odb_expand_ids, which will be populated upon return.