Bug 123316 [Undo] - API BEHAVIOR - should always place a successfully undone/redone op on the redo/undo history
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/DefaultOperationHistory.java
forceUndoLimit(context, limit);
		forceRedoLimit(context, limit);
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.core.commands.operations.IOperationHistory#undo(org.eclipse.core.commands.operations.IUndoContext,
	 *      org.eclipse.core.runtime.IProgressMonitor,
	 *      org.eclipse.core.runtime.IAdaptable)
	 */
	public IStatus undo(IUndoContext context, IProgressMonitor monitor,
			IAdaptable info) throws ExecutionException {
		Assert.isNotNull(context);
		IUndoableOperation operation = getUndoOperation(context);
		
		if (operation == null)
			return IOperationHistory.NOTHING_TO_UNDO_STATUS;
		
		if (!operation.canUndo()) {
			if (DEBUG_OPERATION_HISTORY_UNEXPECTED) {
				Tracing.printTrace("OPERATIONHISTORY", 
						"Undo operation not valid - " + operation); 
			}
			return IOperationHistory.OPERATION_INVALID_STATUS;
		}
		return doUndo(monitor, info, operation);
	}
	/*
	 * (non-Javadoc)
	 *