When using fileExist=Append and tempFileName="someFile" the append option appears to be ignored. This appears to be a result of not being able to append temp file. This can be seen with the tempPrefix as the code will throw an IllegalArgumentException:

throw new IllegalArgumentException("You cannot set both fileExist=Append and tempPrefix options");

This should also occur when the fileExist=Append and tempFileName are specified.

A doc update mentioning this would also be help.