def full_path
      p = self
      until p.prior.nil? || p.prior.library
        p = p.prior
      end
      p.prior.nil? ? p.path : [p.prior] + p.path
    end
def full_path
      p = self
      until p.prior.nil? || p.prior.library
        p = p.prior
      end
      p.prior.nil? ? p.path : [p.prior] + p.path
    end
Unlike path which only gives the path from this environment going forward
  Get the full path, that is go to the HEAD of the path this environment is on
  and then give me that entire path