Allow using '/' as external storage root

Signed-off-by: Robin Appelman <robin@icewind.nl>

apps/files_external/js/settings.js

@@ -960,7 +960,7 @@ MountConfigListView.prototype = _.extend({
 			success: function(result) {
 				var onCompletion = jQuery.Deferred();
 				$.each(result, function(i, storageParams) {
-					storageParams.mountPoint = storageParams.mountPoint.substr(1); // trim leading slash
+					storageParams.mountPoint = (storageParams.mountPoint === '/')? '/' : storageParams.mountPoint.substr(1); // trim leading slash
 					var storageConfig = new self._storageConfigClass();
 					_.extend(storageConfig, storageParams);
 					var $tr = self.newStorage(storageConfig, onCompletion);

apps/files_external/lib/Controller/StoragesController.php

@@ -143,7 +143,7 @@ abstract class StoragesController extends Controller {
 	 */
 	protected function validate(StorageConfig $storage) {
 		$mountPoint = $storage->getMountPoint();
-		if ($mountPoint === '' || $mountPoint === '/') {
+		if ($mountPoint === '') {
 			return new DataResponse(
 				array(
 					'message' => (string)$this->l10n->t('Invalid mount point')