$ nmcli connection add type ethernet con-name t autoconnect no
  Error: ifname argument is required.

This reverts commit a91eafdf ('cli: 'con add': make ifname mandatory
(except bond,bridge,vlan) (bgo #698113)'). Apparently ifname argument was
required to avoid confusion (unexpected behavior). But I don't agree
that is an issue, it's just annoying. Often you really have just one
ethernet or Wi-Fi device, so this does not seem helpful.

NetworkManager/NetworkManager!222