Generate DITAVAL based on installed plug-ins

[jelovirt]

Description

Generate a DITAVAL file based on installed plug-ins, to allow using e.g. props="plugin(org.dita.html5)" to only show content when HTML5 plug-in is installed. Don't enable this in site build, because we want content for all plug-ins on the website.

[infotexture]

@jelovirt Interesting idea, but I'm not sure I understand the use case.

Looking at the code, I understand that this enables content to be included or excluded based on which plug-ins are installed, which might be very useful in certain environments.

However, in our docs, while we have content that is specific to each of the default plug-ins — each of those is always installed, so the content would always be included. If the list of bundled plug-ins changes from one release to another, we remove related content from the docs, so there wouldn't be anything left to exclude.

I do see value in profiling and filtering content by output format, so certain things could be marked as specific to particular output formats (like with @print='no').

— But if I marked up something as peculiar to the site output, with this approach it looks like it would be output even to other formats as long as the site plug-in is installed (which is always the case on my machine, and on CI).

So I'm interested, but I'm not sure I get it yet. 🤔