gfm.rb

  # GitHub Flavored Markdown Layer
  def fix_markdown_quirks(text)
    # prevent foo_bar_baz from ending up with an italic word in the middle
    text.gsub!(/(^(?! {4}|\t)\w+_\w+_\w[\w_]*)/) do |x|
      x.gsub('_', '\_') if x.split('').sort.to_s[0..1] == '__'
    end

    # in very clear cases, let newlines become <br /> tags
    text.gsub!(/(\A|^$\n)(^\w[^\n]*\n)(^\w[^\n]*$)+/m) do |x|
      x.gsub(/^(.+)$/, "\\1  ")
    end

    text
  end