Merge branch 'new-merge-requests-commit-tab-active' into 'master'

MergeRequest new form load diff asynchronously

## What does this MR do?

Don't return diff tab content from the server when request for a new merge request

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

To avoid 502 errors due to this controller action takes to much time

## What are the relevant issue numbers?

Relates #13912

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- ~~[ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- ~~[ ] API support added~~
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5844

1 files changed, 2 insertions, 2 deletions

diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 071dfe54ef9..a743bf313ae 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -31,7 +31,7 @@ class MergeRequest < ActiveRecord::Base
 
   # Temporary fields to store compare vars
   # when creating new merge request
-  attr_accessor :can_be_created, :compare_commits, :compare
+  attr_accessor :can_be_created, :compare_commits, :diff_options, :compare
 
   state_machine :state, initial: :opened do
     event :close do
@@ -196,7 +196,7 @@ class MergeRequest < ActiveRecord::Base
   end
 
   def diff_size
-    merge_request_diff.size
+    diffs(diff_options).size
   end
 
   def diff_base_commit