auto_link_urls

# File actionpack/lib/action_view/helpers/text_helper.rb, line 543
        def auto_link_urls(text, html_options = {})
          link_attributes = html_options.stringify_keys
          text.gsub(AUTO_LINK_RE) do
            href = $&
            punctuation = ''
            left, right = $`, $'
            # detect already linked URLs and URLs in the middle of a tag
            if left =~ /<[^>]+$/ && right =~ /^[^>]*>/
              # do not change string; URL is already linked
              href
            else
              # don't include trailing punctuation character as part of the URL
              if href.sub!(/[^\w\/-]$/, '') and punctuation = $& and opening = BRACKETS[punctuation]
                if href.scan(opening).size > href.scan(punctuation).size
                  href << punctuation
                  punctuation = ''
                end
              end

              link_text = block_given?? yield(href) : href
              href = 'http://' + href unless href =~ %r{^[a-z]+://}i

              content_tag(:a, h(link_text), link_attributes.merge('href' => href)) + punctuation
            end
          end
        end