There should be a way to insert the following content from files into XAR's XML files:
- text nodes from the text content of a file in utf-8 (in any text-oriented position, e.g. page content or object property)
- base64 attachment content from any file
This is probably best done as a transformation extending the XAR Mojo's transformations.
The interest of doing so, is that in multiple cases (such as JS, CSS or velocity code), it is useful to edit the content of the files using an editor that is able to provide developer-services such as auto-completion, syntax coloring, or API-documentation. Moreover, it makes the content being included within the XWiki archive, a first-class citizen so that such tools as versioning systems, their helping hands (diffs and previous notably), and desktop tools can all be used.