The additional-directories property is not supported, but expected

I noticed in the zope log that when running a static deployment, a warning message would appear indicating that the additional-directories property in the staticdeployment.ini was not specified (and therefore assumed it must be expected, and that there might be useful code that would do something with it, if specified.)

I have some directories with many, many media files that are in my theme and not stored in the CMS, and so have a long list of additional-files. I'd rather use this additional-directories directive.

I've attempted to specify this directive, and see that its value (list) appears to be acquired in the code, but I'm not sure it is respected or that anything is done with it.

It would be great to have this directive supported in order to reduce the number of lines specified under the additional-files directive.

There is nothing mentioned of this directive in the README. Is it intended to be supported or not? (As mentioned, there are references in the code.)

If supported, what is the expected syntax? I've supplied a path equal to the file paths used under additional-files (beginning with ++mytheme++/ of my Diazo theme that contains a bunch of media files I need exported), both with and without a trailing slash, but it doesn't seem to export files in that path from the theme.

Your help/insight is appreciated!