magallanes/Mage/Task/BuiltIn/Deployment/Releases.php

<?php
class Mage_Task_BuiltIn_Deployment_Releases
    extends Mage_Task_TaskAbstract
{
    public function getName()
    {
        return 'Releasing [built-in]';
    }

    public function run()
    {
        if ($this->_config->release('enabled', false) == true) {
            $releasesDirectory = $this->_config->release('directory', 'releases');
            $symlink = $this->_config->release('symlink', 'current');

            $currentCopy = $releasesDirectory . '/' . $this->_config->getReleaseId();

            $result = $this->_runRemoteCommand('ln -sf ' . $currentCopy . ' ' . $symlink);
            return $result;

        } else {
            return false;
        }
    }

}