Joining Repositories

Hello everybody, 

we're using git with cogito as a frontend. For some reasons I forgot we have some repositories which belong to the same project. To simplify the whole thing I would like to join these repositories. It mainly means to move some directories. So lets say I have:

	/r1/.git
	/r2/.git

and what I would like to have is

	/r/.git
	   r1
           r2

Of course the history should remain (otherwise it would be to easy). 

How should I do this?

Thanks for your answers

	Mathias