Actually, the worst problem with submodules in modern DVCSs is handling dependencies. If project A depends on project B and project B and the API exposed by pro

Actually, the worst problem with submodules in modern DVCSs is handling dependencies. If project A depends on project B and project B and the API exposed by project B varies over time it is pretty easy to keep both in sync and working. Except, when someone needs to check out an older version of A they need to figure out which version of B to check out (and it might not be as easy as checking out the latest B in the date that that version of A was committed). Git allows you to mark a specific revision of a submodule, but then updating the whole project is no longer a single command, and there are some problems with not pushing everything at the same time.