code: public static String getRelativeURI( HttpServletRequest request, PageFlowController relativeTo )
      {
          if ( relativeTo == null ) return InternalUtils.getDecodedServletPath( request );
          return getRelativeURI( request, InternalUtils.getDecodedURI( request ), relativeTo );
      }
docs: Get the request URI, relative to the URI of the given PageFlowController.
  
  @param request the current HttpServletRequest.
  @param relativeTo a PageFlowController to which the returned URI should be relative, or
  <code>null</code> if the returned URI should be relative to the webapp root.