notes: convert init_notes to use struct object_id

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

notes.c

@@ -993,7 +993,7 @@ const char *default_notes_ref(void)
 void init_notes(struct notes_tree *t, const char *notes_ref,
 		combine_notes_fn combine_notes, int flags)
 {
-	unsigned char sha1[20], object_sha1[20];
+	struct object_id oid, object_oid;
 	unsigned mode;
 	struct leaf_node root_tree;
 
@@ -1017,16 +1017,16 @@ void init_notes(struct notes_tree *t, const char *notes_ref,
 	t->dirty = 0;
 
 	if (flags & NOTES_INIT_EMPTY || !notes_ref ||
-	    get_sha1_treeish(notes_ref, object_sha1))
+	    get_sha1_treeish(notes_ref, object_oid.hash))
 		return;
-	if (flags & NOTES_INIT_WRITABLE && read_ref(notes_ref, object_sha1))
+	if (flags & NOTES_INIT_WRITABLE && read_ref(notes_ref, object_oid.hash))
 		die("Cannot use notes ref %s", notes_ref);
-	if (get_tree_entry(object_sha1, "", sha1, &mode))
+	if (get_tree_entry(object_oid.hash, "", oid.hash, &mode))
 		die("Failed to read notes tree referenced by %s (%s)",
-		    notes_ref, sha1_to_hex(object_sha1));
+		    notes_ref, oid_to_hex(&object_oid));
 
 	hashclr(root_tree.key_sha1);
-	hashcpy(root_tree.val_sha1, sha1);
+	hashcpy(root_tree.val_sha1, oid.hash);
 	load_subtree(t, &root_tree, t->root, 0);
 }