Generate a feed based on an arbitrary list

[pathawks]

If jekyll-feed exposed a public API to generate a feed given an arbitrary set of posts, than other plugins like jekyll-archives would be able choose when to generate category specific feeds and whatnot.

This would add complexity to both jekyll-feed as well as any plugins that decided to take advantage of such a feature (jekyll-archives).

That said, it would be nice if those that wanted different feeds didn't have to reinvent the wheel, and could benefit from the work that has already been done here.

We would have to expose a public API by which a calling plugin could provide an array of posts, a title for the feed, and probably a filename. We would then be responsible for generating the feed.

This is different from #70 in that it only exposes an API that other plugins can call to generate an arbitrary feed, rather than us being responsible for what feeds the user wants built.

I do not imagine that this would be a very popular feature, and hopefully jekyll-archives would default to not generating any extra feeds unless specifically configured to do so, but it does seem to be an oft-requested feature.

jekyll/jekyll-archives#57

[pathawks]

This still seems like a cool idea, but it seems like it would make the code much more complex.

Maybe someday, but not today.