A Liquid tag for Jekyll sites that allows embedding Gists and showing code for non-JavaScript enabled browsers and readers.

gist_tag.rb

require 'cgi'
require 'digest/md5'
require 'net/https'
require 'uri'

module Jekyll
  class GistTag < Liquid::Tag
    def initialize(tag_name, text, token)
      super
      @text           = text
      @cache_disabled = false
      @cache_folder   = File.expand_path "../_gist_cache", File.dirname(__FILE__)
    end

    def render(context)
      if parts = @text.match(/([\d]*) (.*)/)
        gist, file = parts[1].strip, parts[2].strip
        script_url = script_url_for gist, file
        code       = get_cached_gist(gist, file) || get_gist_from_web(gist, file)
        html_output_for script_url, code
      else
        ""
      end
    end

    def html_output_for(script_url, code)
      code = CGI.escapeHTML code
      "<script src='#{script_url}'></script><noscript><pre><code>#{code}</code></pre></noscript>"
    end

    def script_url_for(gist_id, filename)
      "https://gist.github.com/#{gist_id}.js?file=#{filename}"
    end

    def get_gist_url_for(gist, file)
      "https://gist.github.com/raw/#{gist}/#{file}"
    end

    def cache(gist, file, data)
      cache_file = get_cache_file_for gist, file
      File.open(cache_file, "w") do |io|
        io.write data
      end
    end

    def get_cached_gist(gist, file)
      return nil if @cache_disabled
      cache_file = get_cache_file_for gist, file
      File.read cache_file if File.exist? cache_file
    end

    def get_cache_file_for(gist, file)
      bad_chars = /[^a-zA-Z0-9\-_.]/
      gist      = gist.gsub bad_chars, ''
      file      = file.gsub bad_chars, ''
      md5       = Digest::MD5.hexdigest "#{gist}-#{file}"
      File.join @cache_folder, "#{gist}-#{file}-#{md5}.cache"
    end

    def get_gist_from_web(gist, file)
      gist_url          = get_gist_url_for gist, file
      raw_uri           = URI.parse gist_url
      https             = Net::HTTP.new raw_uri.host, raw_uri.port
      https.use_ssl     = true
      https.verify_mode = OpenSSL::SSL::VERIFY_NONE
      request           = Net::HTTP::Get.new raw_uri.request_uri
      data              = https.request request
      data              = data.body
      cache gist, file, data unless @cache_disabled
      data
    end
  end

  class GistTagNoCache < GistTag
    def initialize(tag_name, text, token)
      super
      @cache_disabled = true
    end
  end
end

Liquid::Template.register_tag('gist', Jekyll::GistTag)
Liquid::Template.register_tag('gistnocache', Jekyll::GistTagNoCache)

Now we need to get Github Pages to support something similar... ^_^

+1 on that

+1

In case anyone stumbles here wondering why the noscript portion gets butchered, I think it's from the Markdown parser. (sorry, not really sure)

But you can fix the output by removing the noscript tags and just hiding the pre with javascript instead. That why the page will still show the code if javascript is off, say in RSS feed content for example.

The Markdown parser bug appears to be fixed by adding a newline character between the </script> and <noscript>:

<script src='#{script_url}'></script>\n<noscript><pre><code>#{code}</code></pre></noscript>