The 'gcloud init' command currently only clones a single repo, which is named default. in the future you may be able to host multiple repos, each with their own name.
Also, we may add the ability to nicely import other assets into your project as well, which would not necessarily live in your repo.
So, the primary Google-hosted repository is one asset that is part of your local developer workspace, and since we intend to bring in more in the future, it gets put in its own directory 'default' (which is the name of that repo) so that it does not have conflicts with future assets.