Create a shorcut with GIT into the same repository (similar to SVN externals)

Question

We are migrating projects from SVN to GIT.

I have an issue. In one of the SVN project, they used SVN externals in order to create shortcuts between modules like this :

-ModuleA       
|_ srcA    
-ModuleB    
|_ srcB    
-Common    
|_ srcCommon    
|_ srcA (via externals)    
|_ srcB (via externals)   

When I do a checkout of the svn repository, in my folder Common, I have 3 files.

Admitting that these 3 modules are in the same git repository now (for some budget reasons...), how can I make it similar in git. (from what I understand, subtree or submodule works when having two differents repositories)

Because for now if I clone the git repository, I have :

-ModuleA    
|_ srcA
-ModuleB    
|_ srcB    
-Common    
|_ srcCommon