Say I have a dataset with 100 snapshots and want to
rm -rf all folders named "cache" in all snapshots.
I want to actually free up the space, not just hide it away in layers of snapshots, so making a clone and removing from that and then taking a new snapshot doesn't seem to do what I want.
Any semi-automatical way do that? Some wrapping around zfs list -t snapshot, zfs clone, zfs promote, zfs snapshot?
(cross-posting from http://superuser.com/questions/313197 since I see this has more ZFS stuff)