Is your feature request related to a problem? Please describe.

I think it would be really cool to have the gt rename command tie into the online::service::github stuff to enable renaming of GitHub repositories automatically.

Describe the solution you'd like
That'd likely need a new task::RenameRemote to mirror the existing task::CreateRemote and we probably want to add a config flag + a command line argument to control the behaviour if we do so.

If we did build that, I suspect we'd need to be pretty clever as well about determining a few things:

• Are both repos part of the same service?
• Are both repos part of the same namespace? (If so, rename the repo)
• Are both repos part of different namespaces? (If so, transfer the repo)

The cool part is that if we built that on the existing online::services::* machinery, it would be pretty straightforward to extend it to support other services in future - and it'll automatically support GitHub Enterprise too.