Subversion is a software versioning and revision control system distributed as free software.

Documentation: http://svnbook.red-bean.com

Other useful commands:

• Recursively remove all files in a working copy that are not under version control:
  • svn status | grep ^\? | cut -c9- | xargs –no-run-if-empty -d \\n rm -r

• Checkout specific files only:
  • svn checkout http://svn.svnhost.com/projectX –depth immediates
  • cd projectX
  • svn update –set-depth immediates trunk
  • cd trunk 
  • svn update –set-depth infinity