#!/bin/sh -e

tmp_cleanup() {
  [ -d "$BASE" ] || return
  mountpoint -q "$BASE" || return
  umount -l $BASE
  rmdir $BASE
}

trap "tmp_cleanup" 0 1 2 3 15

BASE=$(mktemp -d)
mount -t tmpfs tmpfs $BASE -o mode=755,size=401276k
mkdir $BASE/delta/ $BASE/.work/ $BASE/root/

if [ "$1" ]; then
  base_dir="$1"
else
  base_dir='/'
fi

mount -t overlay overlay $BASE/root/ \
  -o workdir=$BASE/.work,lowerdir=$base_dir,upperdir=$BASE/delta

systemd-nspawn --setenv=LANG=C.UTF-8 \
  --tmpfs=/tmp/:mode=1777 \
  --bind=/var/cache/apt/archives/ \
  --register=no \
  --directory=$BASE/root/ || true