Commit Briefs
zero also base_id in search_delta_for_object
not sure why it's needed, it should be zeroed by got_pack_parse_ref_delta via got_packfile_extract_raw_delta, but it isn't.
add field to got_packidx to propagate the hash algo
allows to drop all the `algo' hardcodings in lib/pack.c and pack_idx.c
handle both sha1 and sha256 object ids in pack files
bump got_packidx_object_id so it can hold a sha256 digest and adapt the code to read the needed type of hash.