Remove files that are not in subversion

One of the great features of version control is that I can easily revert
back to a known good state. I can do this in
Subversion with the following command:

% svn revert -R .

However, if I have new files that are not in Subversion, this command
will not delete them. Here is a fun ruby one liner to remove those
files:

svn st | ruby -ne 'File.delete($_[1..-1].strip) if $_.match(/^\?/)'

This command loops over svn status and deletes all files from lines that
start with ?.