diff: correct handling of labels. -10 bytes

diff: correct handling of labels. -10 bytes

>>From 05eeb173f0431b4fbed7684d7a9cea42f747f63e Mon Sep 17 00:00:00 2001
From: Matheus Izvekov <mizvekov@gmail.com>
Date: Mon, 18 Jan 2010 20:33:55 -0200
Subject: [PATCH] diff: correct handling of labels

This fixes an issue where diff would apply labels to files in the
inverse order, when using -L or --label.
This fixes it in order to be compatible with gnu diff.
It also makes it not an error to specify more than one label.
The behavior for such cases is that they override the label for the new
file.

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>