diff-no-index.c: use error_errno()

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff-no-index.c

@@ -65,8 +65,7 @@ static int populate_from_stdin(struct diff_filespec *s)
 	size_t size = 0;
 
 	if (strbuf_read(&buf, 0, 0) < 0)
-		return error("error while reading from stdin %s",
-				     strerror(errno));
+		return error_errno("error while reading from stdin");
 
 	s->should_munmap = 0;
 	s->data = strbuf_detach(&buf, &size);