Concurrent Versions System

 CVS is a version control system, which allows you to keep old versions
 of files (usually source code), keep a log of who, when, and why
 changes occurred, etc., like RCS or SCCS. Unlike the simpler systems,
 CVS does not just operate on one file at a time or one directory at
 a time, but operates on hierarchical collections of directories
 consisting of version controlled files.
 .
 CVS helps to manage releases and to control the concurrent editing of
 source files among multiple authors. CVS allows triggers to
 enable/log/control various operations and works well over a wide area
 network.