Bug 162655 [Undo] [IDE] - Undoing a delete should check for existence of resources to be restored
N20061027. - I deleted two projects (along with their content). I read the warning that undo delete cannot restore the content and said "OK." - Then I checked out those same projects from HEAD. - Then I selected "Undo Delete Resources." This overwrote my code with empty projects. I think that "Undo Delete Resources" should become invalid if the resources exist again, because you'll end up replacing content without keeping a backup.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/ide/undo/AbstractResourcesOperation.java
* public API from a background thread.
 * 
 * This class is not intended to be subclassed by clients.
 * 
 * <strong>EXPERIMENTAL</strong> This class or interface has been added as part
 * of a work in progress. This API may change at any given time. Please do not
 * use this API without consulting with the Platform/UI team.
 * 
 * @since 3.3
 * 
 */
abstract class AbstractResourcesOperation extends AbstractWorkspaceOperation {
	/*
	 * The array of resource descriptions known by this operation to create or
	 * restore overwritten resources.
	 */
	protected ResourceDescription[] resourceDescriptions;
	/**
	 * Create an Abstract Resources Operation
	 * 
	 * @param resources
	 *            the resources to be modified
	 * @param label
	 *            the label of the operation
	 */
	AbstractResourcesOperation(IResource[] resources, String label) {
		super(label);
		this.addContext(WorkspaceUndoUtil.getWorkspaceUndoContext());
		setTargetResources(resources);
	}