#!/bin/bash
set -e

mode_subst () {
    $fn >$bfn.new
}

mode_diff () {
    mode_subst
    diff -u $dot $bfn.new || test $? = 1
}

mode_install () {
    mode_subst
    mv -f $bfn.new $dot
}

mode=$1
case "$mode" in
subst|diff|install) ;;
*) echo >&2 'bad mode'; exit 1;
esac
shift

if [ $# = 0 ]; then
   set templates/*.in
fi

for fn in "$@"; do
    bfn=${fn%.in}
    bfn=${bfn##*/}
    bfn=${bfn#.}
    bfn=templates/$bfn
    fn=${bfn}.in
    dot=$HOME/.${bfn#*/}
    mode_$mode
done