auto_link_patch.rb

# Put this file in your config/initializers directory and behold a tastier auto_link!

module ActionView
  module Helpers
    module TextHelper
      # Use auto_link and friends from Rails 3. They do the right thing (tm).

      remove_const(:AUTO_LINK_RE) if defined?(AUTO_LINK_RE)
      AUTO_LINK_RE = %r{
          ( https?:// | www\. )
          [^\s<]+
        }x

      BRACKETS = { ']' => '[', ')' => '(', '}' => '{' }

      def auto_link(text, *args, &block)
        return '' if text.blank?

        options = args.size == 2 ? {} : args.extract_options!
        unless args.empty?
          options[:link] = args[0] || :all
          options[:html] = args[1] || {}
        end
        options.reverse_merge!(:link => :all, :html => {})

        case options[:link].to_sym
          when :all                         then auto_link_email_addresses(auto_link_urls(text, options[:html], &block), options[:html], &block)
          when :email_addresses             then auto_link_email_addresses(text, options[:html], &block)
          when :urls                        then auto_link_urls(text, options[:html], &block)
        end
      end

      private

        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
              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 href =~ %r{^[a-z]+://}i

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

        def auto_link_email_addresses(text, html_options = {})
          body = text.dup
          text.gsub(/([\w\.!#\$%\-+]+@[A-Za-z0-9\-]+(\.[A-Za-z0-9\-]+)+)/) do
            text = $1

            if body.match(/<a\b[^>]*>(.*)(#{Regexp.escape(text)})(.*)<\/a>/)
              text
            else
              display_text = (block_given?) ? yield(text) : text
              mail_to text, display_text, html_options
            end
          end
        end
    end
  end
end

What are the improvements you're making here?

The Rails 3 auto_link has a more sane treatment of URLs, especially regarding punctuation around links and anchor portions of URLs. It fixes some bugs we had on GitHub.

Glad I helped

@mislav: Hah, awesome. Didn't know it was your handywork!