restriction of pulls

Is it possible to restrict a chechout, clone or a later pull to some subdirectory of a repository? (Background: using subversion (or cvs), it is possible to do a file or directory-restricted update.)

Say, I have a repository containing 2 (mostly) independent projects A and B 
(in separate) directories:
- R
  -  A
  -  B
Is it possibly to pull all the changes made to B, but not those made to A. 
(Yes, I know that this causes trouble if there are dependencies into A.)

Regards