Merge branch 'jk/use-oid-pos'

Code clean-up to ensure our use of hashtables using object names as keys use the "struct object_id" objects, not the raw hash values. * jk/use-oid-pos: oid_pos(): access table through const pointers hash_pos(): convert to oid_pos() rerere: use strmap to store rerere directories rerere: tighten rr-cache dirname check rerere: check dirname format while iterating rr_cache directory commit_graft_pos(): take an oid instead of a bare hash