#! /bin/sh
set -ex
if [ $# != 1 ] || ! echo "$1" | grep -q '-';then
  echo >&2 "Syntax: $0 branch-list-delimited-by-dashes"
  exit 1
fi
base="master"
for elem in $(echo "$1"|tr '-' ' ');do
  if [ "$base" = "master" ];then
    next="$elem"
  else
    next="$base-$elem"
  fi
  git checkout "$next"
  git merge "$base"
  if [ -e "$next".patch ];then
    echo -e '/^--- /,$d\nw'|ed "$next".patch
  fi
  git diff "$base" "$next"|diffdecvs >>"$next".patch
  base="$next"
done
echo OK