Bug 89020 [Undo] Operation throws assertion failure if undo limit is set to 0
I20050324-0800 Unfortunately existing clients of text's undo manager were allowed to set any number without failing. This is no longer possible: an assertion failure occurrs if the limit is smaller than 1. I will add code on my side that will handle the negative numbers but the operation history must allow 0.
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/DefaultOperationHistory.java
* information to <code>System.out</code> during the open/close sequence.
	 */
    public static boolean DEBUG_OPERATION_HISTORY_OPENOPERATION = false;
	/**
	 * This flag can be set to <code>true</code> if the history should print
	 * information to <code>System.out</code> whenever an operation is not
	 * approved.
	 */
    public static boolean DEBUG_OPERATION_HISTORY_APPROVAL = false;
	
	protected static final int DEFAULT_LIMIT = 20;
	
	/**
	 * An operation info status describing the condition that there is no available
	 * operation for redo.
	 */
	public static final IStatus NOTHING_TO_REDO_STATUS = new OperationStatus(
			IStatus.INFO, OperationStatus.NOTHING_TO_REDO,
			"No operation to redo"); 
	/**
	 * An operation info status describing the condition that there is no available
	 * operation for undo.
	 */
	public static final IStatus NOTHING_TO_UNDO_STATUS = new OperationStatus(
			IStatus.INFO, OperationStatus.NOTHING_TO_UNDO,
			"No operation to undo"); 
	/**
	 * An operation error status describing the condition that the operation available
	 * for execution, undo or redo is not in a valid state for the action to be
	 * performed.