All files port doesn't provide

[Ryan Schmidt]

Is there an easy way to see all the files in my MacPorts prefix that *aren't* provided by any MacPorts port? Basically the list of files that'd be left if I "sudo port -f uninstall installed", except I don't actually want to uninstall everything to find out. I could probably write a script to find out, by subtracting the output of "port -q contents installed" from the output of "find ${prefix} \! -type d" or something, but if there's something built-in I'd rather use that.