- Patch #700592 by dww: ArchiverTar class supports .tgz but we didn't recognize it.

modules/system/system.module

@@ -3541,7 +3541,7 @@ function system_date_format_delete($dfid) {
 function system_archiver_info() {
   $archivers['tar'] = array(
     'class' => 'ArchiverTar',
-    'extensions' => array('tar', 'tar.gz', 'tar.bz2'),
+    'extensions' => array('tar', 'tgz', 'tar.gz', 'tar.bz2'),
   );
   if (function_exists('zip_open')) {
     $archivers['zip'] = array(