rerere.c: remove implicit dependency on the_index

The reason rerere(), rerere_forget() and rerere_remaining() take a
struct repository instead of struct index_state is not obvious from
the patch:

Deep in update_paths() and find_conflict(), hold_locked_index() and
read_index() are called. These functions assumes the index path at
$GIT_DIR/index which is not always true when you take an arbitrary
index state. Taking a repository will allow us to point to the right
index path later when we replace them with repo_ versions.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/commit.c b/builtin/commit.c
index 0d9828e..bf06fbf 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1651,7 +1651,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 		      "new_index file. Check that disk is not full and quota is\n"
 		      "not exceeded, and then \"git reset HEAD\" to recover."));
 
-	rerere(0);
+	repo_rerere(the_repository, 0);
 	run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 	run_commit_hook(use_editor, get_index_file(), "post-commit", NULL);
 	if (amend && !no_post_rewrite) {