Adding labels when creating PRs on github

[xocasdashdash]

Our CI requires that some labels be present to work correctly.

How do you feel about adding a comma separated list of labels to the when submitting a branch? in my case it's ok to fail if the labels are not present

[abhinav]

This makes sense. It was amongst the "when we need it" features.
I'll try to get to this when I have the time.

The rough shape of this, if you'd like to take a stab at this:

• Add a new field to submitOptions. These are shared across all submit commands. I would make it a []string plus a comma-split through Kong (ref).
• Plumb that to forge.Repository.SubmitChange. Preferably, also to forge.Repository.EditChange.
• In the forge package, adjust forge.Repository's SubmitChange and EditChange methods to support labels (new fields on the request/options structs)
• In github/submit and github/edit, use this information to make GH requests.
• A similar change will be required in shamhub which is our fake GitHub-like service that most of the integration tests are written against.

There may be some nuance to the forge.Repository contract because, I suspect, GitHub labels have to be created before being used, and they're probably not idempotent, and we don't want to make too many extraneous requests.