shopping cart - hide the Cart Quantity Update button when not needed

[dause]

I found it inconvenient that the cart quantity update button is always visible even for articles where the quantity can not be changed.
In such cases the button does not have any function and should better be hidden.

Here is a fix that I created:

in tpl_shopping_cart_default.php look for these lines:

<?php
  if ($product['buttonUpdate'] == '') {
    echo '' ;
  } else {
    echo $product['buttonUpdate'];
  }
?>

and change them to:

<?php
  if ($product['buttonUpdate'] == '' || $product['flagShowFixedQuantity'] ) {
    echo '' ;
  } else {
    echo $product['buttonUpdate'];
  }
?>

BTW: $product['flagShowFixedQuantity'] and $product['showFixedQuantity'] seem identical to me. Is there any reason why there are two fields in the array holding the same information? Thanks!