Bug 105697 [Undo] - OperationHistoryEvent - cannot distinguish between canceled event or failed event
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/OperationHistoryEvent.java
/**
	 * ABOUT_TO_EXECUTE indicates that an operation is about to execute.
	 * Listeners should prepare for the execution as appropriate. Listeners will
	 * receive a DONE notification if the operation is successful, or an
	 * OPERATION_NOT_OK notification if the execution is cancelled or otherwise
	 * fails. This notification is only received for those operations executed
	 * by the operation history. Operations that are added to the history after
	 * execution do not trigger these notifications.
	 * 
	 * If the operation successfully executes, clients will also receive a
	 * notification that it has been added to the history.
	 * 
	 * (value is 1).
	 */
	public static final int ABOUT_TO_EXECUTE = 1;
	/**
	 * ABOUT_TO_REDO indicates that an operation is about to be redone.
	 * Listeners should prepare for the redo as appropriate. Listeners will
	 * receive a REDONE notification if the operation is successful, or an
	 * OPERATION_NOT_OK notification if the redo is cancelled or otherwise
	 * fails.
	 * 
	 * (value is 2).
	 */
	public static final int ABOUT_TO_REDO = 2;
	/**
	 * ABOUT_TO_UNDO indicates that an operation is about to be undone.