Bug 125272 [Viewers] AbstractTreeViewer needs remove(Object parentElement, Object[] childElements)
There is an add(Object parentElement, Object[] childElements) but no corresponding remove(). Without this method, if you have an element that appears under multiple parents, the only way to get model and viewer in sync after removing the element from just one of its parents is calling refresh().
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
* </p>
     * 
     * @param widget
     *           the widget
     * @param element
     *           the element
     * @param doStruct
     *           <code>true</code> if structural changes are to be picked up,
     *           and <code>false</code> if only label provider changes are of
     *           interest
     * @param updateLabels
     *           <code>true</code> to update labels for existing elements,
     *           <code>false</code> to only update labels as needed, assuming
     *           that labels for existing elements are unchanged.
     * @since 3.1
     */
    protected void internalRefresh(Widget widget, Object element,
            boolean doStruct, boolean updateLabels) {
        if (widget instanceof Item) {
            if (doStruct) {
                updatePlus((Item) widget, element);
            }
            if (updateLabels || !equals(element, widget.getData())) {
                doUpdateItem(widget, element, true);
            } else {
                associate(element, (Item) widget);
            }
        }
        if (doStruct) {
            internalRefreshStruct(widget, element, updateLabels);