A couple of weeks back I wrote about using CVS for versioning control. The other widely used technology is called SVN (Subversion). Again, SVN can be managed by command line and in fact you have more control using the command line. If you need to use Subversion occasionally, you can use SmartSVN. The process of using SmartSVN is very similar to using SmartCVS. SVN is a common tool used by Drupal houses to allow many developers and themers access to the same files in development of a site.