builtin: stop using the_index

Convert builtins to use `the_repository->index` instead of `the_index`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/write-tree.c

@@ -3,7 +3,7 @@
  *
  * Copyright (C) Linus Torvalds, 2005
  */
-#define USE_THE_INDEX_VARIABLE
+
 #include "builtin.h"
 #include "config.h"
 #include "environment.h"
@@ -44,8 +44,8 @@ int cmd_write_tree(int argc, const char **argv, const char *cmd_prefix)
 	prepare_repo_settings(the_repository);
 	the_repository->settings.command_requires_full_index = 0;
 
-	ret = write_index_as_tree(&oid, &the_index, get_index_file(), flags,
-				  tree_prefix);
+	ret = write_index_as_tree(&oid, the_repository->index, get_index_file(),
+				  flags, tree_prefix);
 	switch (ret) {
 	case 0:
 		printf("%s\n", oid_to_hex(&oid));