This is probably the reason why I’ll never use Mercurial as a version control system: its complete inability to revert to a known, sane state without deleting and starting all over. No thank you I’d prefer not to have to re-download 10′s of MB of data onto my NFS home dir when I have a perfectly good, already almost perfect copy on disk.

http://stackoverflow.com/questions/2139165/mercurial-delete-all-local-changesets-revert-to-tree