Make default language configurable via config.php

config/config.sample.php

@@ -56,6 +56,9 @@ $CONFIG = array(
 /* Theme to use for ownCloud */
 "theme" => "",
 
+/* Optional ownCLoud default language - overrides automatic language detection on public pages like login or shared items. This has no effect on the users's language preference configured under "personal -> language" once they have logged in */
+"default_language" => "en",
+
 /* Path to the parent directory of the 3rdparty directory */
 "3rdpartyroot" => "",
 
@@ -154,7 +157,7 @@ $CONFIG = array(
 /* Enable/disable X-Frame-Restriction */
 /* HIGH SECURITY RISK IF DISABLED*/
 "xframe_restriction" => true,
-	
+
 /* The directory where the user data is stored, default to data in the owncloud
  * directory. The sqlite database is also stored here, when sqlite is used.
  */

lib/l10n.php

@@ -298,6 +298,12 @@ class OC_L10N{
 			}
 		}
 
+    $default_language = OC_Config::getValue('default_language', false);
+
+    if($default_language !== false) {
+      return $default_language;
+    }
+
 		if(isset($_SERVER['HTTP_ACCEPT_LANGUAGE'])) {
 			$accepted_languages = preg_split('/,\s*/', strtolower($_SERVER['HTTP_ACCEPT_LANGUAGE']));
 			if(is_array($app)) {