When Drupal rolls out a new release, Drush is not equipped to updated the Drupal core. Drush will download the new core for us, but we have to merge the files ourselves. How do we move the core files into production, preserve our contrib and custom modules, all while maintaining our SVN structure?

$ svn rm /path/to/old-drupal                           # Get rid of existing files
$ cd /path/to/new-drupal                               # It's important to be in the new drupal dir so that our relative paths work ok
$ find * -type d -exec mkdir /path/to/old-drupal/{} \; # Mimic the directory structure (ignore any errors)
$ find * -type f -exec cp {} /path/to/old-drupal/{} \; # Copy the new files over
$ svn add /path/to/old-drupal/*                        # Re-add the files