Bug 94438 [Undo] - javadoc - clarify operation remaining in history for undo/redo with INFO/WARNING
The javadoc for the IOperationHistory#undo(...) redo(...) methods is very explicit about the operation remaining in the history on CANCEL and ERROR status, and that it is moved between undo/redo histories when ok. Some minor clarifications: The lack of an explicit statement about INFO and WARNING makes one wonder what happens to the operation. It remains in the history in this case also... Technically, on OK status the operation is not guaranteed to move between the stacks. If it cannot redo after undoing, or cannot undo after redoing, it won't be transferred to the other stack, but in effect will be removed from the history.
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/IOperationHistory.java
* </p>
	 * 
	 * @param approver
	 *            the IOperationApprover to be added as an approver.the instance
	 *            to remove. Must not be <code>null</code>. If an attempt is
	 *            made to register an instance which is already registered with
	 *            this instance, no operation is performed.
	 * 
	 * @see org.eclipse.core.commands.operations.IOperationApprover
	 */
	void addOperationApprover(IOperationApprover approver);
	/**
	 * <p>
	 * Add the specified listener to the list of operation history listeners
	 * that are notified about changes in the history or operations that are
	 * executed, undone, or redone.
	 * </p>
	 * 
	 * @param listener
	 *            the IOperationHistoryListener to be added as a listener. Must
	 *            not be <code>null</code>. If an attempt is made to register
	 *            an instance which is already registered with this instance, no
	 *            operation is performed.
	 * 
	 * @see org.eclipse.core.commands.operations.IOperationHistoryListener
	 * @see org.eclipse.core.commands.operations.OperationHistoryEvent
	 */
	void addOperationHistoryListener(IOperationHistoryListener listener);
	/**
	 * <p>