#!/bin/sh
set -e

case "$1" in
"-N") fwd=-N; rev=-R; verb="applied";;
"-R") fwd=-R; rev=-N; verb="reversed";;
*) echo >&2 "Usage: $0 <-N|-R> <patch-file>"; exit 2;;
esac

if patch --dry-run -F0 -f $rev -p1 < "$2" >/dev/null; then
	echo >&2 "patch already $verb: $2"
	exit 0
fi
patch --dry-run -F0 -f $fwd -p1 < "$2"
patch -F0 -f $fwd -p1 < "$2"