Cache MR diffs result. Improve diff output

Procfile

-web: bundle exec puma -p $PORT
+web: bundle exec unicorn_rails -p $PORT -E development
 worker: bundle exec sidekiq -q post_receive,mailer,system_hook,project_web_hook,common,default,gitlab_shell

app/controllers/projects/merge_requests_controller.rb

@@ -30,7 +30,6 @@ class Projects::MergeRequestsController < Projects::ApplicationController
   end
 
   def diffs
-    @diffs = @merge_request.diffs
     @commit = @merge_request.last_commit
 
     @comments_allowed = @reply_allowed = true

app/models/merge_request.rb

@@ -116,7 +116,7 @@ class MergeRequest < ActiveRecord::Base
   end
 
   def diffs
-    load_diffs(st_diffs) || []
+    @diffs ||= (load_diffs(st_diffs) || [])
   end
 
   def reloaded_diffs
@@ -128,6 +128,8 @@ class MergeRequest < ActiveRecord::Base
 
   def broken_diffs?
     diffs == broken_diffs
+  rescue
+    true
   end
 
   def valid_diffs?

app/views/projects/merge_requests/_show.html.haml

@@ -21,7 +21,8 @@
   .notes.tab-content.voting_notes#notes{ class: (controller.action_name == 'show') ? "" : "hide" }
     = render "projects/notes/notes_with_form"
   .diffs.tab-content
-    = render "projects/merge_requests/show/diffs" if @diffs
+    - if current_page?(action: 'diffs')
+      = render "projects/merge_requests/show/diffs"
   .status
 
 :javascript

app/views/projects/merge_requests/show/_diffs.html.haml

 - if @merge_request.valid_diffs?
-  = render "projects/commits/diffs", diffs: @diffs
+  = render "projects/commits/diffs", diffs: @merge_request.diffs
 - elsif @merge_request.broken_diffs?
   %h4.nothing_here_message
     Can't load diff.

doc/install/installation.md

@@ -184,11 +184,11 @@ You can change `5-3-stable` to `master` if you want the *bleeding edge* version,
     sudo chmod -R u+rwX  public/uploads
 
     # Copy the example Puma config
-    sudo -u git -H cp config/puma.rb.example config/puma.rb
+    sudo -u git -H cp config/unicorn.rb.example config/unicorn.rb
 
     # Enable cluster mode if you expect to have a high load instance
     # Ex. change amount of workers to 3 for 2GB RAM server
-    sudo -u git -H vim config/puma.rb
+    sudo -u git -H vim config/unicorn.rb
 
     # Configure Git global settings for git user, useful when editing via web
     # Edit user.email according to what is set in gitlab.yml
@@ -196,7 +196,7 @@ You can change `5-3-stable` to `master` if you want the *bleeding edge* version,
     sudo -u git -H git config --global user.email "gitlab@localhost"
 
 **Important Note:**
-Make sure to edit both `gitlab.yml` and `puma.rb` to match your setup.
+Make sure to edit both `gitlab.yml` and `unicorn.rb` to match your setup.
 
 ## Configure GitLab DB settings