Bug 89031 [Undo/Redo] IWorkbench#getOperationSupport() marked experimental
IWorkbench#getOperationSupport() marked experimental
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/DefaultOperationHistory.java
/**
	 * An operation info status describing the condition that there is no available
	 * operation for redo.
	 */
	public static final IStatus NOTHING_TO_REDO_STATUS = new OperationStatus(
			IStatus.INFO, OperationStatus.NOTHING_TO_REDO,
			"No operation to redo"); 
	/**
	 * An operation info status describing the condition that there is no available
	 * operation for undo.
	 */
	public static final IStatus NOTHING_TO_UNDO_STATUS = new OperationStatus(
			IStatus.INFO, OperationStatus.NOTHING_TO_UNDO,
			"No operation to undo"); 
	/**
	 * An operation error status describing the condition that the operation available
	 * for execution, undo or redo is not in a valid state for the action to be
	 * performed.
	 */
	public static final IStatus OPERATION_INVALID_STATUS = new OperationStatus(
			IStatus.ERROR, OperationStatus.OPERATION_INVALID,
			"Operation is not valid"); 
	/**
	 * the list of {@link IOperationApprover}s
	 */
	protected List approvers = new ArrayList();
	/**
	 * a map of undo limits per context
	 */
	private HashMap limits = new HashMap();