482 copy instructions

[fsteimke]

See issue #482 Because handling of media files can be complicated, the stylesheets may provide support under certain circumstances. If the destination of the transformation is known within the stylesheets, we can infer the destination for media files as well, and a script with instructions for copying the media files can be created on request. If the expath file:copy function is available, the copy instructions can even be executed.

See new Section 3.4.1 "Copy instructions for media files" in the Reference Guide.