pacdiff: check cmp's exit code rather than output

Signed-off-by: Florian Pritz <bluewind@xinu.at>
Signed-off-by: Allan McRae <allan@archlinux.org>

contrib/pacdiff.sh.in

@@ -92,8 +92,8 @@ while IFS= read -u 3 -r -d '' pacfile; do
 		rm -iv "$pacfile"
 		continue
 	fi
-	check="$(cmp "$pacfile" "$file")"
-	if [ -z "${check}" ]; then
+
+	if cmp -s "$pacfile" "$file"; then
 		echo "  Files are identical, removing..."
 		rm -v "$pacfile"
 	else