For a given port determine its dependencies using any combination of the
 - FETCH_DEPENDS
 - EXTRACT_DEPENDS
 - PATCH_DEPENDS
 - LIB_DEPENDS
 - BUILD_DEPENDS
 - RUN_DEPENDS 

and show them as a pseudo graphical tree.
Use back references for cross-connections.

WWW: http://code.google.com/p/porttree/