[middleman] タグごとに記事の一覧ページを作る

activate :blog do |blog|
  blog.sources = "articles/{title}.html"
  blog.permalink = "articles/{title}.html"
  blog.taglink = "tags/{tag}.html"
  blog.tag_template = "tags.html"
end
<% blog.articles.each do |article| %>
  <% if article.tags.include?(tagname) %>
  <div class="article"><a href="<%= article.url %>"><%= article.title %></a></div>
  <% end %>
<% end %>