disable cleanFolder for the federated share storage

apps/files_sharing/lib/External/Storage.php

@@ -89,8 +89,17 @@ class Storage extends DAV implements ISharedStorage {
 			'user' => $options['token'],
 			'password' => (string)$options['password']
 		));
+	}
 
-		$this->getWatcher()->setPolicy(\OC\Files\Cache\Watcher::CHECK_ONCE);
+	public function getWatcher($path = '', $storage = null) {
+		if (!$storage) {
+			$storage = $this;
+		}
+		if (!isset($this->watcher)) {
+			$this->watcher = new Watcher($storage);
+			$this->watcher->setPolicy(\OC\Files\Cache\Watcher::CHECK_ONCE);
+		}
+		return $this->watcher;
 	}
 
 	public function getRemoteUser() {

apps/files_sharing/lib/External/Watcher.php

@@ -0,0 +1,33 @@
+<?php
+/**
+ * @author Robin Appelman <icewind@owncloud.com>
+ *
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program 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, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+namespace OCA\Files_Sharing\External;
+
+class Watcher extends \OC\Files\Cache\Watcher {
+	/**
+	 * remove deleted files in $path from the cache
+	 *
+	 * @param string $path
+	 */
+	public function cleanFolder($path) {
+		// not needed, the scanner takes care of this
+	}
+}