Level: Adding a fork after cloning upstream

Sometimes people clone before they fork, or they fork, but then clone the upstream repository.

When they do this, they need to add their fork as a remote.

They might use `git remote set-url origin mygit` and `git remote add upstream upstreamurl`.
They may also do `git remote rename origin upstream` and `git remote add origin mygit`.

We should have a level to help them handle this situation.