Index: includes/menu.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/menu.inc,v
retrieving revision 1.362
diff -u -p -r1.362 menu.inc
--- includes/menu.inc	11 Nov 2009 08:28:50 -0000	1.362
+++ includes/menu.inc	24 Nov 2009 21:09:04 -0000
@@ -2343,8 +2343,9 @@ function _menu_navigation_links_rebuild(
           $item['plid'] = $existing_item['plid'];
         }
         else {
-          // If it moved, put it at the top level in the new menu.
-          $item['plid'] = 0;
+          // It moved to a new menu, so let menu_link_save() try to find a
+          // valid parent based on path.
+          unset($item['plid']);
         }
         $item['has_children'] = $existing_item['has_children'];
         $item['updated'] = $existing_item['updated'];
@@ -2543,7 +2544,6 @@ function _menu_delete_item($item, $force
  *   saved.
  */
 function menu_link_save(&$item) {
-
   drupal_alter('menu_link', $item);
 
   // This is the easiest way to handle the unique internal path '<front>',
@@ -2569,14 +2569,12 @@ function menu_link_save(&$item) {
     }
   }
 
+  // The re-parenting process always needs to be invoked, since there is no
+  // guarantee that {menu_links} does not contain stale data caused by a
+  // re-parenting process that went wrong in a previous rebuild.
+  // 'plid' can be 0 (zero) for top-level links in a menu.
   if (isset($item['plid'])) {
-    if ($item['plid']) {
-      $parent = db_query("SELECT * FROM {menu_links} WHERE mlid = :mlid", array(':mlid' => $item['plid']))->fetchAssoc();
-    }
-    else {
-      // Don't bother with the query - mlid can never equal zero..
-      $parent = FALSE;
-    }
+    $parent = db_query("SELECT * FROM {menu_links} WHERE mlid = :mlid", array(':mlid' => $item['plid']))->fetchAssoc();
   }
   else {
     $query = db_select('menu_links');
@@ -2585,10 +2583,9 @@ function menu_link_save(&$item) {
     if ($item['module'] == 'system') {
       $query->condition('module', 'system');
     }
-    else {
-      // If not derived from a router item, we respect the specified menu name.
-      $query->condition('menu_name', $item['menu_name']);
-    }
+    // Always respect the link's menu name. Inheritance for router items is
+    // ensured in _menu_router_build().
+    $query->condition('menu_name', $item['menu_name']);
 
     // Find the parent - it must be unique.
     $parent_path = $item['link_path'];
@@ -2603,6 +2600,7 @@ function menu_link_save(&$item) {
       }
     } while ($parent === FALSE && $parent_path);
   }
+  // If a parent link was found, derive its menu.
   if ($parent !== FALSE) {
     $item['menu_name'] = $parent['menu_name'];
   }
@@ -2636,7 +2634,7 @@ function menu_link_save(&$item) {
       ->execute();
   }
 
-  if (!$item['plid']) {
+  if ($item['plid'] == 0) {
     $item['p1'] = $item['mlid'];
     for ($i = 2; $i <= MENU_MAX_DEPTH; $i++) {
       $item["p$i"] = 0;
@@ -3054,6 +3052,15 @@ function _menu_router_build($callbacks) 
 
         $parent = $menu[$parent_path];
 
+        // Try to inherit the menu name from parent router items.
+        if (!isset($item['menu_name'])) {
+          if (!isset($parent['menu_name'])) {
+            $parent['menu_name'] = db_query("SELECT menu_name FROM {menu_links} WHERE router_path = :router_path", array(':router_path' => $parent_path))->fetchColumn();
+          }
+          if (!empty($parent['menu_name'])) {
+            $item['menu_name'] = $parent['menu_name'];
+          }
+        }
         if (!isset($item['tab_parent'])) {
           // Parent stores the parent of the path.
           $item['tab_parent'] = $parent_path;