Ability to configure default port for tilt up when running a particular Tiltfile

[QAston]

Describe the Feature You Want

I'd love to be able to run 2 different tiltfiles at the same time without having to set different ports using external methods.

I'd love a default_settings(port=20350) tilt declaration which would allow setting a default port, but which would still be overridden by the tilt up --port flag and env variables.

Current Behavior

When you run two distinct tiltfiles with tilt up they clash ports, so you need to wrap tilt to load overriding configuration, for example by loading a .env file.

Why Do You Want This?

This would reduce hassle a bit

[nicks]

Letting the tiltfile change the port seems like it could lead to a ton of sadness if you're trying to debug a build (e.g. if the tiltfile has a local() that fails or a syntax error)

[QAston]

A section in tilt_config.json then?