WIP: Download patch with code comments for unresolved discussions

/cc @rspeicher @smcgivern

Example patch:

From 80ed295019941ebaf3377c7202c9120ea932425e Mon Sep 17 00:00:00 2001
From: Administrator <admin@example.com>
Date: Thu, 30 Mar 2017 17:18:32 -0600
Subject: [PATCH] FIXME: Add code comments for unresolved discussions from
 gitlab-org/gitlab-ce!8

All unresolved non-outdated diff discussions from this merge request are
added in the relevant places as code comments with a 'FIXME' prefix.

This commit was automatically generated by GitLab. Be sure to remove it
from your branch before the merge request is merged.
---
 app/models/user.rb | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/app/models/user.rb b/app/models/user.rb
index 2db35dc2be..5636d1ae11 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -94,6 +94,11 @@ class User < ActiveRecord::Base
   # the user is destroyed. If the user owns any issues during deletion, this
   # should be treated as an exceptional condition.
   has_many :issues,                   dependent: :restrict_with_exception, foreign_key: :author_id
+  # FIXME: Administrator (@root) started a discussion on the previous line:
+  #   Should we do the same for notes?
+  # 
+  # FIXME: Administrator (@root) commented:
+  #   I guess we can do that later
 
   #
   # Validations
@@ -334,6 +339,8 @@ class User < ActiveRecord::Base
       ghost_user ||
         begin
           users = Enumerator.new do |y|
+          # FIXME: Administrator (@root) started a discussion on the previous line:
+          #   This is pretty hard to understand
             n = nil
             loop do
               user = User.new(
-- 
2.11.0

To do:

• Cache commit
• Consider including discussions on deleted lines
• Consider including outdated diff discussions
• Consider including non-diff discussions
• Comments in more languages
• Improve text in modal
• Specs
• Docs