#!/bin/zsh
setopt extendedglob no_unset
cd $0:h/done || exit $?
current=( *(@) )
keep=( $current:A:t )

for d in *(/); do
	if (($+keep[(r)${d:t}])); then
		print -r keep: $d
	else
		btrfs sub del $d
	fi
done