Support new diff notes on MRs with diff_refs

app/controllers/projects/merge_requests_controller.rb

@@ -85,6 +85,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
       noteable_id: @merge_request.id
     }
 
+    @use_legacy_diff_notes = !@merge_request.support_new_diff_notes?
     @grouped_diff_notes = @merge_request.notes.grouped_diff_notes
 
     Banzai::NoteRenderer.render(

app/models/deployment.rb

@@ -11,6 +11,8 @@ class Deployment < ActiveRecord::Base
 
   delegate :name, to: :environment, prefix: true
 
+  after_save :keep_around_commit
+
   def commit
     project.commit(sha)
   end
@@ -26,4 +28,8 @@ class Deployment < ActiveRecord::Base
   def last?
     self == environment.last_deployment
   end
+
+  def keep_around_commit
+    project.repository.keep_around(self.sha)
+  end
 end

app/models/diff_note.rb

@@ -74,7 +74,7 @@ class DiffNote < Note
   private
 
   def supported?
-    !self.for_merge_request?
+    !self.for_merge_request? || self.noteable.support_new_diff_notes?
   end
 
   def set_original_position

app/models/merge_request.rb

@@ -642,6 +642,10 @@ class MergeRequest < ActiveRecord::Base
     merge_commit
   end
 
+  def support_new_diff_notes?
+    diff_refs && diff_refs.complete?
+  end
+
   def keep_around_commit
     project.repository.keep_around(self.merge_commit_sha)
   end