Fucking about with Docker, and I discover Docker contexts for running against a remote host over SSH. This is very cool.

I discover you can use `docker context use` to switch contexts. I don't like this. It's stateful. I'll forget to switch it back. So on a whim, I try `docker --context=other ps` and it works!

Next, I think, "I've got a lot of shell scripts that use Docker and I don't want to rewrite them. Can I use an environment variable?"

`DOCKER_CONTEXT=other docker ps`

And it works!

I just guessed these; I didn't read a man page.

That's how you design a CLI.