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
* visually expanded! You may have to call <code>parent.setExpanded(true)</code>.
     * </p>
     * 
     * @param widget
     *           the widget
     */
    protected void createChildren(final Widget widget) {
        final Item[] tis = getChildren(widget);
        if (tis != null && tis.length > 0) {
            Object data = tis[0].getData();
            if (data != null)
                return; 
        }
        BusyIndicator.showWhile(widget.getDisplay(), new Runnable() {
            public void run() {
                
                
                if (tis != null) {
                    for (int i = 0; i < tis.length; i++) {
                        if (tis[i].getData() != null) {
                            disassociate(tis[i]);
                            Assert.isTrue(tis[i].getData() == null,
                                    "Second or later child is non -null");
                        }
                        tis[i].dispose();
                    }
                }
                Object d = widget.getData();
                if (d != null) {
                    Object parentElement = d;