anchor.diff:      NewPids = case sets:is_element(Pid, State#state.pids) of
           false -> State#state.pids;
           true ->
  -            self() ! tick, 
  +            self() ! tick,
               sets:del_element(Pid, State#state.pids)
       end,
       {noreply, State#state{ pids = NewPids }};
  
positive.code: 
  handle_info(tick, State) ->
      ThisPid = self(),
      {Now, UpstreamBaseUrls} = upstream_to_be_refreshed(State),
      Pids = case UpstreamBaseUrls of
          [UpstreamBaseUrl| _] -> 
              Pid = spawn_link(fun() -> refresh_upstream(ThisPid, Now, UpstreamBaseUrl) end),
              [Pid];
  
negative.code:     NewUpstream = dict:store(UpstreamBaseUrl, At, State#state.upstream),
      {noreply, State#state{ upstream = NewUpstream, tbd=NewTbd }};
  
  handle_info({upstream_failed, At, UpstreamBaseUrl, _ErrorType, _Reason}, State) ->
      NewUpstream = dict:store(UpstreamBaseUrl, At, State#state.upstream),
      {noreply, State#state{ upstream = NewUpstream }};
  
  handle_info({tarball_done, _At, _BaseUrl, AuthorAndModule, Version}, State) ->
      NewTbd = dict:erase({AuthorAndModule, Version}, State#state.tbd),
  