projects.el and nested projects

[Ergus]

Hi Dmitry:

I am working in a project with a nested setup (like an onion with 3 and
4 levels... VS way). I am wondering how could nested projects be
supported in project.el. I know they were somehow in the past and now
there is the project-external-roots, but I it does not look very used.

So the project root should be the top-most common directory?? Or is
better to use the local/closer one in order to have better scope, and
the add all the others as project-external-roots??

As the original project was for VS studio, I plan to create a sort of
project.el backend for my use case, but I would like to know in advance
a bit if it worth the effort.

Best,
Ergus