wireproto: enable optional args for known() for future extensibility Firstly, I think we should do this for all new wire commands, just to be on the safe side. So I want to get this into the 1.9 release. Secondly, there actually is potential here that sometimes the server can know that the number of its nodes which can possibly still be undecided on the client is small. It might then just send them along directly (cutting short the end game). This, however, requires walking the graph on the server, which can be expensive, so for the moment we're not actually doing it.