Merge branch 'jc/replacing'

Merge branch 'jc/replacing'

* jc/replacing:
  read_sha1_file(): allow selective bypassing of replacement mechanism
  inline lookup_replace_object() calls
  read_sha1_file(): get rid of read_sha1_file_repl() madness
  t6050: make sure we test not just commit replacement
  Declare lookup_replace_object() in cache.h, not in commit.h

Conflicts:
	environment.c