DRY mentioned in magic note constant

app/models/note.rb

@@ -80,7 +80,7 @@ class Note < ActiveRecord::Base
       note_options = {
         project: project,
         author: author,
-        note: "_mentioned in #{gfm_reference}_",
+        note: cross_reference_note_content(gfm_reference),
         system: true
       }
 
@@ -174,7 +174,7 @@ class Note < ActiveRecord::Base
                 where(noteable_id: noteable.id)
               end
 
-      notes.where('note like ?', "_mentioned in #{gfm_reference}_").
+      notes.where('note like ?', cross_reference_note_content(gfm_reference)).
         system.any?
     end
 
@@ -182,8 +182,16 @@ class Note < ActiveRecord::Base
       where("note like :query", query: "%#{query}%")
     end
 
+    def cross_reference_note_prefix
+      '_mentioned in '
+    end
+
     private
 
+    def cross_reference_note_content(gfm_reference)
+      cross_reference_note_prefix + "#{gfm_reference}_"
+    end
+
     # Prepend the mentioner's namespaced project path to the GFM reference for
     # cross-project references.  For same-project references, return the
     # unmodified GFM reference.
@@ -249,6 +257,10 @@ class Note < ActiveRecord::Base
     nil
   end
 
+  def cross_reference?
+    note.start_with?(self.class.cross_reference_note_prefix)
+  end
+
   def find_diff
     return nil unless noteable && noteable.diffs.present?
 

app/services/notification_service.rb

@@ -119,7 +119,7 @@ class NotificationService
 
     # ignore gitlab service messages
     return true if note.note =~ /\A_Status changed to closed_/
-    return true if note.note =~ /\A_mentioned in / && note.system == true
+    return true if note.cross_reference? && note.system == true
 
     opts = { noteable_type: note.noteable_type, project_id: note.project_id }