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>
	 * The severity code in the returned status describes whether the operation
	 * succeeded and whether it remains in the history. <code>OK</code>
	 * severity indicates that the redo operation was successful and that the
	 * operation has been placed on the undo history. Listeners will receive the
	 * <code>REDONE</code> notification.
	 * </p>
	 * <p>
	 * Other severity codes (<code>CANCEL</code, <code>ERROR</code>, <code>INFO</code>,
	 * etc.) are not specifically interpreted by the history.  The operation will remain
	 * in the history and the returned status is simply passed back to the
	 * caller. For all severities other than <code>OK</code>, listeners
	 * will receive the <code>OPERATION_NOT_OK</code> notification
	 * instead of the <code>REDONE</code> notification.
	 * </p>
	 * 
	 * @throws ExecutionException
	 *             if an exception occurred during redo.
	 *
	 */
	IStatus redo(IUndoContext context, IProgressMonitor monitor, IAdaptable info)
			throws ExecutionException;
	/**
	 * <p>
	 * Redo the specified operation
	 * </p>
	 * 
	 * @param operation
	 *            the operation to be redone