Subtrees are nice for some use cases. But that's the very problem, there's no general (and supported out-of-the-box) solution to the problem. DVCSes have solved

Subtrees are nice for some use cases. But that's the very problem, there's no general (and supported out-of-the-box) solution to the problem. DVCSes have solved the distributed development part for one (sub)project, but we currently don't have a compelling solution for distributed development across several (sub)projects.