/**
  * Set the available quantity for a given item.
  *
  * @param Mage_CatalogInventory_Model_Stock_Item
  * @param int $quantity the amount to set
  * @return bool true if the quantity has changed for this product
  */
 protected function updateProductQuantity(Mage_CatalogInventory_Model_Stock_Item $stockItem, $quantity)
 {
     $oldQty = $stockItem->getQty();
     $change = $oldQty !== $quantity;
     if ($change) {
         $stockItem->setQty($quantity);
     }
     return $change;
 }