Merge branch 'jk/core-use-replace-refs'

A new configuration variable core.usereplacerefs has been added,
primarily to help server installations that want to ignore the
replace mechanism altogether.

* jk/core-use-replace-refs:
  add core.usereplacerefs config option
  check_replace_refs: rename to read_replace_refs
  check_replace_refs: fix outdated comment

builtin/index-pack.c

@@ -1680,7 +1680,7 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix)
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage(index_pack_usage);
 
-	check_replace_refs = 0;
+	read_replace_refs = 0;
 	fsck_options.walk = mark_link;
 
 	reset_pack_idx_option(&opts);