Merge branch 'ds/disable-replace-refs' into next

Introduce a mechanism to disable replace refs globally and per
repository.

* ds/disable-replace-refs:
  repository: create read_replace_refs setting
  replace-objects: create wrapper around setting
  repository: create disable_replace_refs()
  pack-bitmap.c: use commit boundary during bitmap traversal
  pack-bitmap.c: extract `fill_in_bitmap()`
  object: add object_array initializer helper function

git.c

@@ -187,7 +187,7 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
 			if (envchanged)
 				*envchanged = 1;
 		} else if (!strcmp(cmd, "--no-replace-objects")) {
-			read_replace_refs = 0;
+			disable_replace_refs();
 			setenv(NO_REPLACE_OBJECTS_ENVIRONMENT, "1", 1);
 			if (envchanged)
 				*envchanged = 1;