Always create merge_request_diff if MR created

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/controllers/projects/merge_requests_controller.rb

@@ -76,7 +76,6 @@ class Projects::MergeRequestsController < Projects::ApplicationController
     @merge_request.author = current_user
     @target_branches ||= []
     if @merge_request.save
-      @merge_request.reload_code
       redirect_to [@merge_request.target_project, @merge_request], notice: 'Merge request was successfully created.'
     else
       @source_project = @merge_request.source_project

app/models/merge_request.rb

@@ -30,7 +30,9 @@ class MergeRequest < ActiveRecord::Base
   belongs_to :target_project, foreign_key: :target_project_id, class_name: "Project"
   belongs_to :source_project, foreign_key: :source_project_id, class_name: "Project"
+
   has_one :merge_request_diff, dependent: :destroy
+  after_create :create_merge_request_diff
   delegate :commits, :diffs, :last_commit, :last_commit_short_sha, to: :merge_request_diff, prefix: nil

app/observers/merge_request_observer.rb

@@ -6,7 +6,6 @@ class MergeRequestObserver < ActivityObserver
       create_event(merge_request, Event.determine_action(merge_request))
     end
-    merge_request.create_merge_request_diff
     notification.new_merge_request(merge_request, current_user)
     merge_request.create_cross_references!(merge_request.project, current_user)
     execute_hooks(merge_request)

lib/api/merge_requests.rb

@@ -88,7 +88,6 @@ module API
           end
           if merge_request.save
-            merge_request.reload_code
             present merge_request, with: Entities::MergeRequest
           else
             handle_merge_request_errors! merge_request.errors