dub fetch should consider git submodules

[wilzbach]

If a package has git submodules, they are usually required to build the project.

For example for the Dlang Tour all translations are submodules, see e.g. this issue.

IIRC dub just uses the GitHub archive tool to download a depedency, but I heard (e.g. #632, #104) that there are plans to use e.g. libgit2, s.t. a proper, recursive git clone can be done.

I couldn't find any specific issue for this, but I think it belongs to "native git support" milestone.

[LunaTheFoxgirl]

Idea: Could dub itself check for .gitmodules in the project and its dependencies so that it could fetch the submodules before building everything?

Would be really useful.

[Geod24]

I made a (hopefully complete enough) proposal for submodules support at #1840 .
While that proposal is much bigger than what is described here, I think having half-supported submodules support does not make much sense, so I propose to move the discussion there.
Feel free to re-open and argue if you think this should be a feature / issue of its own :)