t / t4013 / diff.diff_--no-index_--raw_--no-abbrev_dir2_diron commit should_pack_ref(): new function, extracted from `files_pack_refs()` (531cc4a)
   1$ git diff --no-index --raw --no-abbrev dir2 dir
   2:000000 100644 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000 A      dir/sub
   3$