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  check_replace_refs: fix outdated comment

git.c

@@ -164,7 +164,7 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
 			if (envchanged)
 				*envchanged = 1;
 		} else if (!strcmp(cmd, "--no-replace-objects")) {
-			check_replace_refs = 0;
+			read_replace_refs = 0;
 			setenv(NO_REPLACE_OBJECTS_ENVIRONMENT, "1", 1);
 			if (envchanged)
 				*envchanged = 1;