notes_merge_commit(): do not pass temporary buffer to other function

It is unsafe to pass a temporary buffer as an argument to
read_directory().

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Acked-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

notes-merge.c

@@ -680,7 +680,7 @@ int notes_merge_commit(struct notes_merge_options *o,
 	 * Finally store the new commit object SHA1 into 'result_sha1'.
 	 */
 	struct dir_struct dir;
-	const char *path = git_path(NOTES_MERGE_WORKTREE "/");
+	char *path = xstrdup(git_path(NOTES_MERGE_WORKTREE "/"));
 	int path_len = strlen(path), i;
 	const char *msg = strstr(partial_commit->buffer, "\n\n");
 
@@ -720,6 +720,7 @@ int notes_merge_commit(struct notes_merge_options *o,
 			    result_sha1);
 	OUTPUT(o, 4, "Finalized notes merge commit: %s",
 	       sha1_to_hex(result_sha1));
+	free(path);
 	return 0;
 }