new software in contrib

[neves@ils.nwu.edu (David Neves)]

I put "rcs.lisp" in the contrib directory of cambridge.apple.com.  It is a
quick hack that I put together to manage the editing of project files by
multiple people.  Project files are kept on a central server machine and
users copy those files to their own machine to edit.  

Some documentation:
On any large project there is a danger of 2 people editing the same file at
the same time.  Most likely one person's changes will be lost.  This
software allows someone to "lock" a file so that no one else can edit it. 
When the user is finished editing the file they can "unlock" the file so
that others can edit it.

Approach:
I experimented with a couple of ways of "locking" a file but the one I
ended up with was software based and does not use any operating system
features.  When a file is locked its name is saved in a common file.  When
something else tries to edit the same file (and they are using this
software to grab it) they get a warning message that the file is locked.

We used it quite a bit last year and found it very useful.  It is not
industrial strength software but we haven't had an major problems with it. 
I would appreciate any notification of bugs found.

Enjoy,
-David Neves