Empty node pruning
Specify the -e option to disable pruning. For example, if you copy to a repetition but a previous repetition has not been created, an empty node is created by the engine. This assigns the value to the correct repetition. The engine prunes these by default.
For example:
COPY =x -> root(0).child(2).#text
This statement creates
root(0).child(1).#text
as an empty node.