For the past 8 years I’ve taken advantage of the many powerful features of CVS (Concurrent Versions Systems) to upgrade my Web apps and FreeBSD ports. Nothing could be easier than moving into the application’s shell root and via a simple cvs command… voila! Seconds later the whole shebang is upgraded and customized files remain untouched! Wow!
Well, since then things have changed and most popular Web applications like WordPress, osCommerce, CMS Made Easy now use SVN (Subversion), a version control system. SVN is the most compatible successor to CVS. SVN is not much different than CVS in principle. Though if you did not originally install your app (e.g. WordPress) via SVN, then a simple copying of files is needed as detailed on Installing • Updating WordPress with Subversion
In addition to being convenient it is also has it perks as listed on WP Create and WP Mass Upgrade