I don't know of one - that's kind of why I'm asking. I don't think it's at all unfeasible (I think ZFS might do it, never tried it out) and I think it would be

I don't know of one - that's kind of why I'm asking. I don't think it's at all unfeasible (I think ZFS might do it, never tried it out) and I think it would be an amazing development. I think the unix model of one-purpose programs helps collaboration, maintenance, and produces higher quality programs. I just also think that because they're working in an environment that allows pretty simplistic interop (streams of bytes) and generally provides no history of changes, they tend to be fragile when used in concert, and brutally unforgiving when used alone. If you could undo stuff easily, suddenly the 'brutal, unforgiving' part goes away, and it would enable a much more relaxing, explorative atmosphere, while also meaning people don't have to do stuff like 'alias rm=mv -t ~/.Trash' or whatever.