Code to find the length to uniquely abbreviate object names based
on packfile content, which is a relatively recent addtion, has been
optimized to use the same fan-out table.
* ds/bsearch-hash:
sha1_name: use bsearch_pack() in unique_in_pack()
sha1_name: use bsearch_pack() for abbreviations
packfile: define and use bsearch_pack()
sha1_name: convert struct min_abbrev_data to object_id