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/IOperationHistory.java
* operations are in the order that they would be redone if successive
	 * "Redo" commands were invoked.
	 * 
	 * @param context -
	 *            the context for the redo
	 * @return the array of operations in the history
	 */
	IUndoableOperation[] getRedoHistory(IUndoContext context);
	/**
	 * Get the operation that will next be redone in the given context. This
	 * method is used to retrieve the label or description as needed for the
	 * "Redo" menu.
	 * 
	 * @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);
	/**
	 * 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.
	 * 
	 * @param context -
	 *            the context for the undo
	 * @return the array of operations in the history
	 */
	IUndoableOperation[] getUndoHistory(IUndoContext context);