There are many
Software Configuration Management (SCM) systems also called Revision Control Systems and trillion other names
....
Being a Sun employee, I've been using Teamware ever since I joined Sun. During the development of JDK 6, I became involved in integrating JSR-223 reference implementation (RI) code into JDK 6 (javax.script package and Rhino based JavaScript engine). During this effort, I had to learn CVS - because the RI code was kept in CVS repository.
In a recently started project, we have started using Subversion. I read The Subversion book. When I say I "read", I mean I read it just enough for working with a repository. I don't attempt to read to become an expert - I've not done that with Teamware either!
But, OpenSolaris uses Mercurial. Also, OpenJDK will use Mercurial. So, I woke up finally and started learning Mercurial
I found the following resources very useful:
I hope I won't have to learn yet another SCM before 2015