Add "cron.php" for background jobs. It is named cron.php because more people will recognize the purpose of the file then.

cron.php

@@ -0,0 +1,51 @@
+<?php
+/**
+* ownCloud
+*
+* @author Jakob Sack
+* @copyright 2012 Jakob Sack owncloud@jakobsack.de
+*
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
+* License as published by the Free Software Foundation; either
+* version 3 of the License, or any later version.
+*
+* This library is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU AFFERO GENERAL PUBLIC LICENSE for more details.
+*
+* You should have received a copy of the GNU Affero General Public
+* License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+*
+*/
+
+$RUNTIME_NOSETUPFS = true;
+require_once('lib/base.php');
+
+$appmode = OC_Appconfig::getValue( 'core', 'backgroundjob_mode', 'web' );
+if( OC::$CLI ){
+	if( $appmode == 'web' ){
+		OC_Appconfig::setValue( 'core', 'backgroundjob_mode', 'cron' );
+	}
+
+	// check if backgroundjobs is still running
+	$pid = OC_Appconfig::getValue( 'core', 'backgroundjob_pid', false );
+	if( $pid !== false ){
+		// FIXME: check if $pid is still alive (*nix/mswin). if so then exit
+	}
+	// save pid
+	OC_Appconfig::setValue( 'core', 'backgroundjob_pid', getmypid());
+
+	// Work
+	OC_BackgroundJob_Worker::doAllSteps();
+}
+else{
+	if( $appmode == 'web' ){
+		OC_JSON::error( array( 'data' => array( 'message' => 'Backgroundjobs are using system cron!')));
+		exit();
+	}
+	OC_BackgroundJob_Worker::doNextStep();
+	OC_JSON::success();
+}
+exit();