git overlay not in the root

[spanevin]

Is it possible to specify git source for an overlay which is not in the root of a repository?

I can't find any docs about it.

All examples say something like https://github.com/user/repository.git and I assume that the repository must have portage dir in the root.

But I have portage dir not in the root but somewhere like contrib/gentoo/portage

How can I specify such type of source in a repository description .xml file ?