How can I sort posts by tags in Jekyll?

I'm not familiar with Ruby and I know there's a common Jekyll plugin for doing this but I tried all day and have not been able to get it working.

I added this plugin:

module Jekyll
  class TagIndex < Page
    def initialize(site, base, dir, tag)
      @site = site
      @base = base
      @dir = dir
      @name = 'index.html'
      self.process(@name)
      self.read_yaml(File.join(base, '_layouts'), 'tag_index.html')
      self.data['tag'] = tag
      tag_title_prefix = site.config['tag_title_prefix'] || 'Posts Tagged &ldquo;'
      tag_title_suffix = site.config['tag_title_suffix'] || '&rdquo;'
      self.data['title'] = "#{tag_title_prefix}#{tag}#{tag_title_suffix}"
    end
  end
  class TagGenerator < Generator
    safe true
    def generate(site)
      if site.layouts.key? 'tag_index'
        dir = site.config['tag_dir'] || 'tag/tag'
        site.tags.keys.each do |tag|
          write_tag_index(site, File.join(dir, tag), tag)
        end
      end
    end
    def write_tag_index(site, dir, tag)
      index = TagIndex.new(site, site.source, dir, tag)
      index.render(site.layouts, site.site_payload)
      index.write(site.dest)
      site.pages << index
    end
  end
end

and to _config.yml I added

tag_dir: /tag

I display the list of tags with this include file:

<div class="tags modal">
    <ul>
        {% for tag in site.tags %}
        <li>
            <a href="/tag/{{ tag | first | slugize }}/">
                {{ tag | first }}
            </a>
        </li>
        {% endfor %}
    </ul>
</div>

And when I try to select a tag, the url changes appropriately but nothing else changes. It does not display my tag_index template or filter the tags.

The site can be previewed and full source is available here. I've been banging my head against the wall for a while and can't for the damned of me figure out what I'm not doing right.

Solution

Only some plugins are supported by github pages. Your tag pages are not currently generated.

If you want to use your tag plugin, you have to

generate you site locally
add an empty .nojekyll file
push the generated files in you master branch
you can also push you code in an other branch like code