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>
	 * Get the array of operations in the redo history for a given context. The
	 * operations are in the order that they would be redone if successive
	 * "Redo" commands were invoked.
	 * </p>
	 * 
	 * @param context
	 *            the context for the redo
	 * @return the array of operations in the history
	 */
	IUndoableOperation[] getRedoHistory(IUndoContext context);
	/**
	 * <p>
	 * Get the operation that will next be redone in the given context.
	 * </p>
	 * 
	 * @param context
	 *            the context for the redo
	 * @return the operation to be redone or <code>null</code> if there is no
	 *         operation available. There is no guarantee that the returned
	 *         operation is valid for redo.
	 */
	IUndoableOperation getRedoOperation(IUndoContext context);
	/**
	 * <p>
	 * Get the array of operations that can be undone in the specified context.
	 * The operations are in the order that they would be undone if successive
	 * "Undo" commands were invoked.
	 * </p>