commit 1d90b8be2cfa57ecb81e8d15ae187709858c2bfa
Author: James Wilson <jwilson3@220177.no-reply.drupal.org>
Date:   Tue Mar 5 16:33:35 2013 -0500

    Cache-controlled logo and favicon.

diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 3051560..c748c5b 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1436,32 +1436,48 @@ function theme_get_setting($setting_name, $theme = NULL) {
         }
       }
 
+      // A dummy query-string is added to filenames, to gain control over
+      // browser-caching. The string changes on every update or full cache
+      // flush, forcing browsers to load a new copy of the files, as the
+      // URL changed.
+      $query_string = variable_get('css_js_query_string', '0');
+
       // Generate the path to the logo image.
       if ($cache[$theme]['toggle_logo']) {
+        $logo_path = '';
         if ($cache[$theme]['default_logo']) {
-          $cache[$theme]['logo'] = file_create_url(dirname($theme_object->filename) . '/logo.png');
+          $logo_path = file_create_url(dirname($theme_object->filename) . '/logo.png');
         }
         elseif ($cache[$theme]['logo_path']) {
-          $cache[$theme]['logo'] = file_create_url($cache[$theme]['logo_path']);
+          $logo_path = file_create_url($cache[$theme]['logo_path']);
+        }
+        if (!empty($logo_path)) {
+          $query_string_separator = (strpos($logo_path, '?') !== FALSE) ? '&' : '?';
+          $cache[$theme]['logo'] = $logo_path . $query_string_separator . $query_string;
         }
       }
 
       // Generate the path to the favicon.
       if ($cache[$theme]['toggle_favicon']) {
+        $favicon_path = '';
         if ($cache[$theme]['default_favicon']) {
           if (file_exists($favicon = dirname($theme_object->filename) . '/favicon.ico')) {
-            $cache[$theme]['favicon'] = file_create_url($favicon);
+            $favicon_path = file_create_url($favicon);
           }
           else {
-            $cache[$theme]['favicon'] = file_create_url('core/misc/favicon.ico');
+            $favicon_path = file_create_url('core/misc/favicon.ico');
           }
         }
         elseif ($cache[$theme]['favicon_path']) {
-          $cache[$theme]['favicon'] = file_create_url($cache[$theme]['favicon_path']);
+          $favicon_path = file_create_url($cache[$theme]['favicon_path']);
         }
         else {
           $cache[$theme]['toggle_favicon'] = FALSE;
         }
+        if (!empty($favicon_path)) {
+          $query_string_separator = (strpos($favicon_path, '?') !== FALSE) ? '&' : '?';
+          $cache[$theme]['favicon'] = $favicon_path . $query_string_separator . $query_string;
+        }
       }
     }
   }