Git dependency and git modules

[metacoma]

Describe the bug/feature
As i can understand, at this moment there is no way to clone git repository with git submodules?

To Reproduce

1. define dependency, for example, kapicorp/kapitan git repository

---
parameters: 
  kapitan:
    dependencies:
       - type: git 
         output_path: files/git/github/kapicorp/kapitan
         source: https://github.com/kapicorp/kapitan
         ref: master

$ kapitan compile --fetch

3. Try to open .gitmodules file https://github.com/kapicorp/kapitan/blob/master/.gitmodules

$ ls -ltr files/git/github/kapicorp/kapitan/.gitmodule
ls: cannot access 'files/git/github/kapicorp/kapitan/.gitmodule': No such file or directory

Expected behavior
kapicorp/kapitan github repository must be cloned with git modules (in this case with https://github.com/kapicorp/reclass.git)

Additional context
As far as i understand, kapitan uses GitPython library to clone git repos. Probably, the properly submodule handling in GitPython will helps https://gitpython.readthedocs.io/en/0.3.3/tutorial.html#submodule-handling

Also, submodule option might be added into dependency definition, like

---
parameters: 
  kapitan:
    dependencies:
       - type: git
         submodule: True 
         output_path: files/git/github/kapicorp/kapitan
         source: https://github.com/kapicorp/kapitan
         ref: master