I have two repo A and B. First i checkout repo A to my Eulen directory. 

It contain module folder with some modules. Now i want to take updates of repository B to modules folder in my Eulen->modules folder. 

So my question is when i go for taking modules from repo B, it is cleaning up the modules folder of my directory and putting modules in repo B.

For instead of replacing the modules folder, i just needed the modules of repo B with already existing modules in modules folder.

How can i perform checkout of modules from repo B to modules folder with replacing already existing modules?

Regards