Speedup DiffNote#active? on discussions, preloading noteables and avoid touching git repository to return diff_refs when possible

- Preloading noteable we share the same noteable instance when more than one 
discussion refers to the same noteable.
- Any other call to that object that is cached in that object will be for any 
discussion.
- In those cases where merge_request_diff has all the sha stored to build a diff_refs get that 
diff_refs using directly those sha instead accessing to the git repository to first get the 
commits and later the sha.

1 files changed, 4 insertions, 0 deletions

diff --git a/app/helpers/notes_helper.rb b/app/helpers/notes_helper.rb
index 0c47abe0fba..26bde2230a9 100644
--- a/app/helpers/notes_helper.rb
+++ b/app/helpers/notes_helper.rb
@@ -92,6 +92,10 @@ module NotesHelper
     project.team.max_member_access_for_user_ids(user_ids)
   end
 
+  def preload_noteable_for_regular_notes(notes)
+    ActiveRecord::Associations::Preloader.new.preload(notes.select { |note| !note.for_commit? }, :noteable)
+  end
+
   def note_max_access_for_user(note)
     note.project.team.human_max_access(note.author_id)
   end