How to setup a master merc repo that acts like cvs model

[Harry Putnam]

I run a number of HOSTS, all have there own merc repo for assorted
system related files and assorted home grown scripts.

All of this is very small potatoes compared to what many users here do
with merc.

Of course. my assorted merc repos all grow their own way although
they share many duplicated files.  As you might imagine different OS's
may require some scripts to be edited or require a new script
altogether and so forth.

I'd like to have a master repo that contains all the host repos.

Something like I once did with cvs.  Where each distributed repo is a
checked out module from the master-repo

Can anyone tell me or maybe post a brief summary of how I might set
this up?  Or should I simply go back to using cvs for this?