On the flip side, you can have multiple filesystem entries (via hard links) to the same set of files and set up your own playground directory while keeping a mirror view of the same directory. Remove a file from dir A, and it's still in dir B. Once you're satisfied with the result, you can delete the entire dir B. Accidentally removed a file from A? Restore it from B by making another hard link. (Caveat: hard links don't work with directories unless you're Apple TimeMachine)