Fix commits atom feed

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/views/projects/commits/show.atom.builder

@@ -3,7 +3,7 @@ xml.feed "xmlns" => "http://www.w3.org/2005/Atom", "xmlns:media" => "http://sear
   xml.title   "Recent commits to #{@project.name}:#{@ref}"
   xml.link    :href => project_commits_url(@project, @ref, format: :atom), :rel => "self", :type => "application/atom+xml"
   xml.link    :href => project_commits_url(@project, @ref), :rel => "alternate", :type => "text/html"
-  xml.id      project_commits_url(@project)
+  xml.id      project_commits_url(@project, @ref)
   xml.updated @commits.first.committed_date.strftime("%Y-%m-%dT%H:%M:%SZ") if @commits.any?
   @commits.each do |commit|