#!/bin/sh

set -e -u

help () {
  cat <<EOF
Usage: $0 FILE1 FILE2...
Compare successive pairs of files.
The result is written to FILE1.diff, etc.
EOF
}

if [ $# -eq 0 ] || [ "$1" = "--help" ]; then
  help
  exit
fi

while [ $# -gt 1 ]; do
  diff -ru -- "$1" "$2" >"${2%/}.diff" || [ $? -eq 1 ]
  shift
done