WIP: Autolink URLs in blobs and diffs

Extracted from https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4121.

Contains three attempts/approaches at autolinking:

• 134c848c
• 86c54979
• 798d3289

None of these have acceptable performance.

To do

• Make sure blob rendering performance doesn't suffer dramatically
• Don't run pre-processing pipeline, because this may break the highlighting

lib/banzai/filter/autolink_filter.rb

@@ -26,7 +26,7 @@ module Banzai
       # in the generated link.
       #
       # Rubular: http://rubular.com/r/cxjPyZc7Sb
-      LINK_PATTERN = %r{([a-z][a-z0-9\+\.-]+://\S+)(?<!,|\.)}
+      LINK_PATTERN = %r{([a-z][a-z0-9\+\.-]+://\S+)(?<![,."':?!&)<>])}
       # Text matching LINK_PATTERN inside these elements will not be linked
       IGNORE_PARENTS = %w(a code kbd pre script style).to_set
@@ -54,15 +54,13 @@ module Banzai
       #
       # `@doc` will be re-parsed with the HTML String from Rinku.
       def rinku_parse
-        # Convert the options from a Hash to a String that Rinku expects
-        options = tag_options(link_options)
-
         # NOTE: We don't parse email links because it will erroneously match
         # external Commit and CommitRange references.
         #
         # The final argument tells Rinku to link short URLs that don't include a
         # period (e.g., http://localhost:3000/)
-        rinku = Rinku.auto_link(html, :urls, options, IGNORE_PARENTS.to_a, 1)
+        mode = context[:autolink_emails] ? :all : :urls
+        rinku = Rinku.auto_link(html, mode, tag_options(link_options), IGNORE_PARENTS.to_a, 1)
         return if rinku == html
@@ -111,9 +109,9 @@ module Banzai
         # order to be output literally rather than escaped.
         match.gsub!(/((?:&[\w#]+;)+)\z/, '')
         dropped = ($1 || '').html_safe
-        options = link_options.merge(href: match)
-        content_tag(:a, match, options) + dropped
+        match = ERB::Util.html_escape_once(match)
+        %{<a href="#{match}" #{tag_options(link_options)}>#{match}</a>#{dropped}}.html_safe
       end
       def autolink_filter(text)