Subversion is a version control system described by its authors as a "compelling replacement" for CVS. Like CVS, Subversion uses client-server model. However, Subversion features atomic commits across the repository and allows repository access over the HTTP and WebDAV protocols. Although Subversion has no notion of branches, the branches can be created as copies of the project tree on the server. Such copies are "cheap copies" - they take very little space on the server.
Subversion is available on most modern Linux distributions. The command is called "svn".