Merge branch 'mh/ref-api'

* mh/ref-api:
  clear_ref_cache(): inline function
  write_ref_sha1(): only invalidate the loose ref cache
  clear_ref_cache(): extract two new functions
  clear_ref_cache(): rename parameter
  invalidate_ref_cache(): expose this function in the refs API
  invalidate_ref_cache(): take the submodule as parameter
  invalidate_ref_cache(): rename function from invalidate_cached_refs()

diff --cc refs.c
Simple merge