auto_discovery_link_tag generating an href tag

For some obscure reason, <%= auto_discovery_link_tag %> generates the
following html code:
<link href="" rel="alternate" title="RSS"
type="application/rss+xml" />

This is wrong html. Where does the problem come from? Bug from Rails

By the way,

  <%= stylesheet_link_tag("screen") %>


<link href="/stylesheets/screen.css" media="screen" rel="stylesheet"
type="text/css" />

I smell something bad.

Isn't that supposed to be the behavior of stylesheet_link_tag as per

You are write. However, shouldn't it be <link rel=... ???

Because with <link href=... for the CSS, my validator says it is not
valid html.

It validates okay using the W3C validation service: