tree-walk.c: remove the_repo from fill_tree_descriptor()

While at there, clean up the_repo usage in builtin/merge-tree.c a tiny
bit.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/notes.c b/notes.c
index 532ec37..2522b87 100644
--- a/notes.c
+++ b/notes.c
@@ -397,7 +397,7 @@ static void load_subtree(struct notes_tree *t, struct leaf_node *subtree,
 	struct name_entry entry;
 	const unsigned hashsz = the_hash_algo->rawsz;
 
-	buf = fill_tree_descriptor(&desc, &subtree->val_oid);
+	buf = fill_tree_descriptor(the_repository, &desc, &subtree->val_oid);
 	if (!buf)
 		die("Could not read %s for notes-index",
 		     oid_to_hex(&subtree->val_oid));