Merge branch 'nd/the-index-final'

The assumption to work on the single "in-core index" instance has
been reduced from the library-ish part of the codebase.

* nd/the-index-final:
  cache.h: flip NO_THE_INDEX_COMPATIBILITY_MACROS switch
  read-cache.c: remove the_* from index_has_changes()
  merge-recursive.c: remove implicit dependency on the_repository
  merge-recursive.c: remove implicit dependency on the_index
  sha1-name.c: remove implicit dependency on the_index
  read-cache.c: replace update_index_if_able with repo_&
  read-cache.c: kill read_index()
  checkout: avoid the_index when possible
  repository.c: replace hold_locked_index() with repo_hold_locked_index()
  notes-utils.c: remove the_repository references
  grep: use grep_opt->repo instead of explict repo argument

builtin/pack-objects.c

@@ -970,7 +970,7 @@ static int no_try_delta(const char *path)
 
 	if (!check)
 		check = attr_check_initl("delta", NULL);
-	git_check_attr(&the_index, path, check);
+	git_check_attr(the_repository->index, path, check);
 	if (ATTR_FALSE(check->items[0].value))
 		return 1;
 	return 0;