#!/bin/sh

set -e

removes () {
	rm -f -- "$vardir/snap-mount" "$vardir/snap-device"
}

vardir="$2"

case "$#.$1" in
2.drop)
	fs="$(readlink "$vardir/snap-mount")"
	removes
	mount -vo remount,rw "$fs" || true
	;;
4.snap)
	removes
	mount -vo remount,ro "$4"
	ln -s -- "$3" "$vardir/snap-device"
	ln -s -- "$4" "$vardir/snap-mount"
	;;
*)
	cat >&2 <<'END'
usage: .../remount snap VARDIR DEV MOUNT
       .../remount drop VARDIR
END
	exit 1
	;;
esac