Sorry to answer my own question again. I read the source and open/close is supported.
$ mosquitto_pub -m “Button” -t “myog/IN”
I’m listening with MQTT in another window and sure enough:
18:37:26 Garage door OPEN
Very cool. So now I can control the door via web API or MQTT from anywhere on my network. Now to get something working with HTTPs and IPv6 (I’d rather not use someone else’s cloud).