Bug 302441 [LinkedResources][CommonNavigator] When to show "Files and Folders Operation" dialog on drop
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/navigator/NavigatorDropAdapter.java
public NavigatorDropAdapter(StructuredViewer viewer) {
        super(viewer);
    }
    /*
     * @see org.eclipse.swt.dnd.DropTargetListener#dragEnter(org.eclipse.swt.dnd.DropTargetEvent)
     */
    public void dragEnter(DropTargetEvent event) {
        if (FileTransfer.getInstance().isSupportedType(event.currentDataType)
                && event.detail == DND.DROP_DEFAULT) {
            
            event.detail = DND.DROP_COPY;
        }
        super.dragEnter(event);
    }
    /**
     * Returns an error status with the given info.
     */
    private IStatus error(String message) {
        return error(message, null);
    }
    /**
     * Returns an error status with the given info.
     */
    private IStatus error(String message, Throwable exception) {
        return new Status(IStatus.ERROR, PlatformUI.PLUGIN_ID, 0, message,
                exception);
    }
    /**
     * Returns the actual target of the drop, given the resource
     * under the mouse.  If the mouse target is a file, then the drop actually