Multi-User Source Code Managers ?

[Peter Silva]

I'm looking for a portable source code manager that lets multiple users
modify the same file at the same time.  Two+ users should be
able to get the same mod file (via command like SCCS "get"),
make changes, and only know that someone else was working on 
the same file if the two happen to modify the same LINES of code.

In that case, an error message would be given when the second modifier
of the lines tried to return his mod (using a command like SCCS 'delta').

The manager should also maintain multiple variations of a single package.
The most obvious example of a 'variation' is for hardware dependencies, but
there are many others. We would like to be able to make changes that 
affect a specific number (one, some, all) variations.  

RCS and SCCS meet neither of these requirements. Public domain, shareware
and commercial software are all of interest.   

I have read a paper about SUN's translucent file system which sounded 
interesting, and elegantly supports multiple versions.  I don't remember
it dealing with concurrent editing.  

Experiences, recommendations, etc... wanted.  Will post result if sufficient
interest shown. Advance thanks for your help.

Peter Silva				OS Support
psilva at cid.aes.doe.ca		        Dorval Computer Centre 
					Atmospheric Environment Service

-- 
Peter Silva
psilva at cid.aes.doe.ca
(514) 421-4692