Gitlab `group/namespace/repo` repo support

[pgronkievitz]

What doesn't work

I wanted to try out the CLI, but it seems to be not fully compatible with how we organize repos at work. On the same instance repo organized as owner/repo works flawlessly

Steps to reproduce

1. clone repo from some gitlab instance with group/namespace/repo organization
2. try to run e.g. forge repo view
3. Error: getting repo group/namespace: not found

Additional info

both repos are in a detached head state, as I'm using jj-vcs, but this doesn't seem to affect this case

[andrew]

thanks for reporting, pr over here: #71