How do I?

Run a command?

const stage = new Image("busybox");
stage.run("ls -l /");

Add an environment variable?

const stage = new Image("busybox");
stage.env("KEY", "VALUE");

Pass build arguments?

You can't yet unfortunately

Set an entrypoint?

const stage = new Image("busybox");
stage.entrypoint("/entry");

Add a label to an image?

const stage = new Image("busybox");
stage.label("KEY", "VALUE");

Change the working directory?

const stage = new Image("busybox");
stage.workdir("/app");