notes: make get_note return pointer to struct object_id

Make get_note return a pointer to a const struct object_id.  Add a
defensive check to ensure we don't accidentally dereference a NULL
pointer.

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

1 files changed, 1 insertions, 1 deletions

diff --git a/notes.h b/notes.h
index 6651673ae1..c72bb97106 100644
--- a/notes.h
+++ b/notes.h
@@ -140,7 +140,7 @@ int remove_note(struct notes_tree *t, const unsigned char *object_sha1);
  *
  * Return NULL if the given object has no notes.
  */
-const unsigned char *get_note(struct notes_tree *t,
+const struct object_id *get_note(struct notes_tree *t,
 		const unsigned char *object_sha1);
 
 /*