Further refinement of @jcemer's modifications at <https://gist.github.com/courtenay/5454972#comment-912976> Strictly speaking, we're generating [URI fragments](http://en.wikipedia.org/wiki/Fragment_identifier), not permalinks.

github_style_titles.rb

require 'redcarpet'
module Redcarpet::Render
  class GithubStyleTitles < Base
    #
    # FIXME: this is a temporary workaround until the
    #        following (merged) pull request is included
    #        in the next gem release of Redcarpet 3:
    #        https://github.com/vmg/redcarpet/pull/186
    #
    def header(title, level)
      fragment = title.downcase.gsub(/\W+/, '-')

      # make the fragment unique by appending an incremented counter
      @fragments ||= []
      if @fragments.include? fragment
        fragment += '_1'
        fragment = fragment.next while @fragments.include? fragment
      end
      @fragments << fragment

      # generate HTML for this header containing the above fragment
      [?\n,

        %{<a name="#{fragment}" href="##{fragment}" class="anchor">},
          %{<span class="anchor-icon">},
          '</span>',
        '</a>',

        %{<h#{level} id="#{fragment}">},
          title,
        "</h#{level}>",

      ?\n].join
    end
  end
end

STDOUT

$ irb
## ruby 2.0.0p247 (2013-06-27 revision 41674) [x86_64-linux]
>> require './github_style_titles.rb'
true
>> gh = Redcarpet::Render::GithubStyleTitles.new
#<Redcarpet::Render::GithubStyleTitles:0x00000001cc3a48>
>> puts Redcarpet::Markdown.new(gh).render "test\n\n# test 1\n\n# test 2\n\n# test 1\n\n# test 1"

<a name="test-1" href="#test-1" class="anchor"><span class="anchor-icon"></span></a><h1 id="test-1">test 1</h1>

<a name="test-2" href="#test-2" class="anchor"><span class="anchor-icon"></span></a><h1 id="test-2">test 2</h1>

<a name="test-1_1" href="#test-1_1" class="anchor"><span class="anchor-icon"></span></a><h1 id="test-1_1">test 1</h1>

<a name="test-1_2" href="#test-1_2" class="anchor"><span class="anchor-icon"></span></a><h1 id="test-1_2">test 1</h1>
nil
>>

Thanks dude, worked like a charm for my use case!