Adding git submodule that contains another submodule?

I'm working on a project in one 开发者_运维百科git repository (A) that is including another git repository (B), which in turn includes a third git repository (C). In A, I added B via:

git submodule add https://github.com/blt04/sfDoctrine2Plugin.git plugins/sfDoctrine2Plugin

Click here, and you can see where B references C: https://github.com/doctrine/doctrine2

After doing my git submodule add, my plugins/sfDoctrine2Plugin/lib/vendor/doctrine folder (should contain C) is empty. I tried doing a git submodule update --recursive as per this StackOverflow answer, but it still didn't import the files to that path. I'm at a loss as to what to do here.

You need to do git submodule update --init --recursive. The problem here is the submodule C is never being initialized in the first place.