Bug 94400 [Undo] - After successful undo, should operation be disposed by framework if it cannot be redone?
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/DefaultOperationHistory.java
* (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) {
				System.out
						.print("OPERATIONHISTORY >>> Undo operation not valid - ");  
				System.out.print(operation);
				System.out.println();
			}
			return IOperationHistory.OPERATION_INVALID_STATUS;
		}
		return doUndo(monitor, info, operation);
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.core.commands.operations.IOperationHistory#undoOperation(org.eclipse.core.commands.operations.IUndoableOperation,
	 *      org.eclipse.core.runtime.IProgressMonitor,