if [ \! "$#" = 2 ]; then
	. usage todir fromdir
fi

todir="$1" ; fromdir="$2"  # like vimdiff, not cp

( for D in "$fromdir" "$todir"; do ( cd "$D"; find . -type f; ); done ; ) |
sort -u |
while read F; do
	vimdiff "$todir/$F" "$fromdir/$F"
done