daemon: Support systemd-style socket activation....* nix/nix-daemon/guix-daemon.cc (SD_LISTEN_FDS_START): New macro.
(systemd_activation_sockets): New function.
(main): Use it. Remove obsolete 'printMsg' call.
* doc/guix.texi (Invoking guix-daemon): Document socket activation.
Ludovic Courtès
2021-03-17
daemon: Correctly handle '--discover' with no value....Previously, we'd get:
$ guix-daemon --discover
error: basic_string::_M_construct null not valid
* nix/nix-daemon/guix-daemon.cc (parse_opt): Change second argument to
'settings.set' to properly handle case where ARG is NULL.