Merge branch 'sb/object-store-replace'

Hotfix.

* sb/object-store-replace:
  get_main_ref_store: BUG() when outside a repository
  object.c: clear replace map before freeing it
  replace-object.c: remove the_repository from prepare_replace_object
  object.c: free replace map in raw_object_store_clear

diff --cc refs.c
Simple merge

diff --cc replace-object.c
Simple merge