source/layouts/documentation.erb

<% content_for :page_title do %>
Documentation
<% end %>
<% wrap_layout :layout do %>
<div class="col-md-12 documentation">
<%=
  # Create a variable for the release being rendered.
  url_match = /\/documentation\/([^\/]+)(\/.*)/.match(current_page.url)
  rendering_release = url_match.captures[0]
  doc_page = url_match.captures[1]
  nil
=%>
<h5 class="page-header text-uppercase">Documentation
<select onChange="window.location.href='/documentation/' + this.value + '<%= doc_page =%>'"
        value="<%= rendering_release =%>">
  <% data.downloads.releases.each_with_index do |release, i| %>
  <option value="<%= release.version %>"
    <% if release.version == rendering_release %>selected="selected"<% end %>>
    <%= release.version %>
    <% if i == 0 %>
      (latest)
    <% end %>
  </option>
  <% end %>
</select>
</h5>
<%= yield %>
</div>
<% end %>