Allow discarding file to be undone

It would be good if 'discard' operations where undoable.

I was just preparing some files to commit, and accidentally hit the 'discard' button when I meant to hit 'discard hunk', and appear to have now permanently lost my changes (well, until I go delving through time machine).

Apparently I'm not the first person to do this:

http://stackoverflow.com/questions/11418429/how-to-undo-discard-if-not-committed

If it's not possible/easy to undo, leaving a copy of the file somewhere it could be recovered from manually would be useful (unless that already happens and I just don't know where to look!).