code: func (s *session) AdvertisedReferences() (*packp.AdvRefs, error) {
  	if s.advRefs != nil {
  		return s.advRefs, nil
  	}
  
  	ar := packp.NewAdvRefs()
  	if err := ar.Decode(s.Stdout); err != nil {
  		if err := s.handleAdvRefDecodeError(err); err != nil {
  			return nil, err
  		}
  	}
  
  	transport.FilterUnsupportedCapabilities(ar.Capabilities)
  	s.advRefs = ar
  	return ar, nil
  }
docs: // AdvertisedReferences retrieves the advertised references from the server.