notes: empty notes should be shown by 'git log'

If the user has gone through the trouble of explicitly adding an empty
note, then "git log" should not silently skip it (as if it didn't exist).

Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

notes.c

@@ -1218,8 +1218,7 @@ static void format_note(struct notes_tree *t, const unsigned char *object_sha1,
 	if (!sha1)
 		return;
 
-	if (!(msg = read_sha1_file(sha1, &type, &msglen)) || !msglen ||
-			type != OBJ_BLOB) {
+	if (!(msg = read_sha1_file(sha1, &type, &msglen)) || type != OBJ_BLOB) {
 		free(msg);
 		return;
 	}

t/t3301-notes.sh

@@ -1274,4 +1274,16 @@ append -C "$empty_blob"
 edit
 EOF
 
+test_expect_success 'empty notes are displayed by git log' '
+	test_commit 17th &&
+	git log -1 >expect &&
+	cat >>expect <<\EOF &&
+
+Notes:
+EOF
+	git notes add -C "$empty_blob" --allow-empty &&
+	git log -1 >actual &&
+	test_cmp expect actual
+'
+
 test_done