* guix/scripts/publish.scm (show-help, %options): Add --listen.
(getaddrinfo*): New procedure.
(%default-options): Add 'address'.
(open-server-socket): Replace 'addr' and 'port' with 'address', a
sockaddr.
(guix-publish): Adjust accordingly. Augment "publishing" message with
the actual address.
* doc/guix.texi (Invoking guix publish): Document it.