title: on macports, what ports are supported by 'port select'?
body: <p>I know 'port select' works with gcc and python --> is there a way to get a full list of all the ports that are switchable by 'port select'?</p>
  
  <p>(I want to make a generic 'select' util that delegates to rvm, port select, etc. and quickly let's me switch entire toolset chains)</p>
  
  <p>thanks!</p>