[SOLVED] Page Alternate URLs include Slug

I have a single page, /archive, that I use to list all the posts on my site. The template is in layouts/archive/single.html, which works great. I want to add an Atom feed there, so I created layouts/archive/feed.xml and added it to the front matter of the index.html. It works great, except for the URL. I expect it to be /archive/feed.xml, but instead it’s /archive/index/feed.xml. Why is it inserting that extra index path segment? Thinking it might be the slug, I tried setting a permalink to archive = "/:section/", but it didn’t change it. Is there some other way to get it to exclude the slug from the URL — especially since the index.html is properly generated without it?

BTW, when I tried changing the base name for the Atom output format to index instead of feed, I got the right URL. Is there some sort of special code around the index base name in the application that makes it do this?

While eating lunch, I figured out a workaround: I put url: /archive/ into the front matter. That solved the problem Still feels a bit weird the way index is treated, though.