fixup! diff: ensure consistent diff behavior with ignore options

Author: gitster

diff.c

@@ -2444,7 +2444,7 @@ static int fn_out_consume(void *priv, char *line, unsigned long len)
 	return 0;
 }
 
-static int quick_consume(void *priv, char *line, unsigned long len)
+static int quick_consume(void *priv, char *line UNUSED, unsigned long len UNUSED)
 {
 	struct emit_callback *ecbdata = priv;
 	struct diff_options *o = ecbdata->opt;