I'm thinking about the case where a project already exists with this name.  Instead of generating a new project that will fail at the point where we try to register it, we should detect this error immediately and recommend using a different name, or using `mortar projects:clone PROJECTNAME` to check out that project.

Can you add that?  I think you'd need to get the list of projects the same way `mortar projects` does and check whether the new project name exists in there.

We'll want a test for this case too.