Fix notes for commits inside MR being squashed in one discussion

app/controllers/notes_controller.rb

@@ -71,7 +71,6 @@ class NotesController < ProjectResourceController
 
   # Helps to distinguish e.g. commit notes in mr notes list
   def note_for_main_target?(note)
-    note.for_wall? ||
     (@target_type.camelize == note.noteable_type && !note.for_diff_line?)
   end
 end

app/models/note.rb

@@ -88,7 +88,7 @@ class Note < ActiveRecord::Base
   end
 
   def discussion_id
-    @discussion_id ||= [:discussion, noteable_type.try(:underscore), noteable_id, line_code].join("-").to_sym
+    @discussion_id ||= [:discussion, noteable_type.try(:underscore), noteable_id || commit_id, line_code].join("-").to_sym
   end
 
   # Returns true if this is a downvote note,