Index: feedapi.module
===================================================================
--- feedapi.module	(revision 17461)
+++ feedapi.module	(working copy)
@@ -344,6 +344,25 @@
 }
 
 /**
+ * Implementation of hook_diff().
+ */
+function feedapi_diff(&$old_node, &$new_node) {
+  $result = array();
+  if (isset($old_node->feed->url) || isset($new_node->feed->url)) {
+    $result['attachment'] = array(
+      '#name' => t('Feed URL'),
+      '#old' => array($old_node->feed->url),
+      '#new' => array($new_node->feed->url),
+      '#weight' => 30,
+      '#format' => array(
+        'show_header' => FALSE,
+      )
+    );
+  }
+  return $result; 
+}
+
+/**
  * Implementation of hook_form_alter().
  */
 function feedapi_form_alter(&$form, $form_state, $form_id) {