For p2phttp support in forgejo-aneksajo I decided to just spawn a git annex p2phttp --wideopen server, do authentication on the Forgejo side, and then proxy requests to p2phttp. Since p2phttp only supports serving one repository at the moment this means that I have to allocate one free port per repository. Actually finding a free port adds complexity and a race condition, as there also seems to be no way to set --port 0 for p2phttp and then figure out which port it bound to.
This would be simplified if p2phttp could listen on unix domain sockets instead.
That might be hard to implement, since it uses servant to do the http serving and that probably does not have a way to listen to a unix domain socket.
Is this needed any more since p2phttp does support serving multiple repositories?