auto_link_urls

# File actionpack/lib/action_view/helpers/text_helper.rb, line 460
        def auto_link_urls(text, html_options = {}, options = {})
          link_attributes = html_options.stringify_keys
          text.gsub(AUTO_LINK_RE) do
            scheme, href = $1, $&
            punctuation = []

            if auto_linked?($`, $')
              # do not change string; URL is already linked
              href
            else
              # don't include trailing punctuation character as part of the URL
              while href.sub!(/[^\w\/-]$/, '')
                punctuation.push $&
                if opening = BRACKETS[punctuation.last] and href.scan(opening).size > href.scan(punctuation.last).size
                  href << punctuation.pop
                  break
                end
              end

              link_text = block_given?? yield(href) : href
              href = 'http://' + href unless scheme

              unless options[:sanitize] == false
                link_text = sanitize(link_text)
                href      = sanitize(href)
              end
              content_tag(:a, link_text, link_attributes.merge('href' => href), !!options[:sanitize]) + punctuation.reverse.join('')
            end
          end.html_safe
        end