cannot generate assets timestamp out of stylesheets directory

[Robbin Fan (范凯)]

stylesheet_link_tag did not generate asset timestamp out of stylesheets directory

<%= stylesheet_link_tag '/skins/default/document', '/skins/default/content' %>
<%= stylesheet_link_tag '/skins/default/github', 'hightlight/github.min' %>

output:

<link href="/skins/default/document.css" media="screen" rel="stylesheet" type="text/css" />
<link href="/skins/default/content.css" media="screen" rel="stylesheet" type="text/css" />
<link href="/skins/default/github.css" media="screen" rel="stylesheet" type="text/css" />
<link href="/stylesheets/hightlight/github.min.css?1361078060" media="screen" rel="stylesheet" type="text/css" />