/**
  * Attempt to backup each of the update manifest files by copying them to a file with the same name with a .bak
  * extension. If there is an exception thrown, we attempt to roll back all of the changes.
  *
  * @param string $unzipFolder
  * @param string $handle
  *
  * @return bool
  */
 private function _backupFiles($unzipFolder, $handle)
 {
     $manifestData = UpdateHelper::getManifestData($unzipFolder, $handle);
     try {
         foreach ($manifestData as $row) {
             if (UpdateHelper::isManifestVersionInfoLine($row)) {
                 continue;
             }
             // No need to back up migration files.
             if (UpdateHelper::isManifestMigrationLine($row)) {
                 continue;
             }
             $rowData = explode(';', $row);
             $filePath = IOHelper::normalizePathSeparators(($handle == 'craft' ? craft()->path->getAppPath() : craft()->path->getPluginsPath() . $handle . '/') . $rowData[0]);
             // It's a folder
             if (UpdateHelper::isManifestLineAFolder($filePath)) {
                 $folderPath = UpdateHelper::cleanManifestFolderLine($filePath);
                 if (IOHelper::folderExists($folderPath)) {
                     Craft::log('Backing up folder ' . $folderPath, LogLevel::Info, true);
                     IOHelper::createFolder($folderPath . '.bak');
                     IOHelper::copyFolder($folderPath . '/', $folderPath . '.bak/');
                 }
             } else {
                 // If the file doesn't exist, it's probably a new file.
                 if (IOHelper::fileExists($filePath)) {
                     Craft::log('Backing up file ' . $filePath, LogLevel::Info, true);
                     IOHelper::copyFile($filePath, $filePath . '.bak');
                 }
             }
         }
     } catch (\Exception $e) {
         Craft::log('Error updating files: ' . $e->getMessage(), LogLevel::Error);
         UpdateHelper::rollBackFileChanges($manifestData, $handle);
         return false;
     }
     return true;
 }