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
IOverwriteQuery {
    /**
     * A flag indicating that overwrites should always occur.
     */
    private boolean alwaysOverwrite = false;
    /**
     * The last valid operation.
     */
    private int lastValidOperation = DND.DROP_NONE;
    /**
     * Constructs a new drop adapter.
     * 
     * @param viewer the navigator's viewer
     */