auto_discovery_link_tag(フォードの種類, [URLオプション, オプション])
<%= auto_discovery_link_tag %>
# <link href="http://localhost:3000/" rel="alternate" title="RSS" type="application/rss+xml" />
<%= auto_discovery_link_tag(:atom) %>
# <link href="http://localhost:3000/" rel="alternate" title="ATOM" type="application/rss+xml" />
<%= auto_discovery_link_tag(:rss, {controller: "pages", action: "feed"}) %>
# <link href="http://localhost:3000/pages/feed" rel="alternate" title="RSS" type="application/rss+xml" />
<%= auto_discovery_link_tag(:rss, "http://www.example.com/feed.rss", {title: "Example RSS"}) %>
# <link href="http://www.example.com/feed.rss" rel="alternate" title="Example RSS" type="application/rss+xml" />