Drush has integration with SVN which makes it easy to update a module and automatically commit the new version of the code to SVN.
In this example we use Drush to update a fictional module named "modulename" and then commit the changes to SVN along with a commit message for the SVN log:

drush up modulename --svnsync --svncommit --svnmessage="svn commit message."

To update all outdated Drupal core and contrib modules modules:

drush up --svnsync --svncommit --svnmessage="svn commit message."