Preref parser for auto-detected title, description and details

[gaborcsardi]

The registered parsers are only called if the @title, @description and @details tags are used explicitly, but not if they are just extracted from the first and second paragraphs and the rest.

It would be great if they could be called from process_description as well.

[hadley]

PR would be great :)

[gaborcsardi]

This part is a bit messy in roxygen. First the file is split on @, and all tags call their preref parsers. The initial part does not have a @ tag, so that is left out from this process, and passed along as introduction. Then, at a higher level, process_description is called, which splits this initial part into @title, @description and @details.

@details is especially tricky, because process_description merges the @details tag (if present) with the leftover of the intro, so the preref parser is sometimes only called on part of the real @details.

I think the splitting done in process_description should be done in parse.preref, conceptually. Instead of or in addition to just passing along introduction. As I see it, this is a clean change, process_description does not do anything else in addition to the splitting.

Please let me know if I am missing something.

[hadley]

That seems reasonable to me.