More and more software development is done by teams that rely on version control systems to share the source code and work together. Researchers also frequently use version control systems to cooperate on writing articles. CVS that was the defacto standard in the early days has been replaced in many environments by subversion. Recently, git and mercurial were proposed as a better alternative to subversion. In a recent article published by ACM Queue, Brian O'Sullivan provides an informative comparison of the advantages and drawbacks of these version control systems : http://queue.acm.org/detail.cfm?id=1595636