Merge branch 'fix-mention-notification' into 'master'

Fix Mention notification level.

Fixes internal issue https://dev.gitlab.org/gitlab/gitlabhq/issues/2236.

See merge request !527

app/services/notification_service.rb

@@ -131,21 +131,24 @@ class NotificationService
       recipients << note.commit_author
     end
     
-    # Get users who left comment in thread
-    recipients = recipients.concat(noteable_commenters(note))
+    # Add all users participating in the thread (author, assignee, comment authors)
+    participants = 
+      if target.respond_to?(:participants)
+        target.participants
+      elsif target.is_a?(Commit)
+        author_ids = Note.for_commit_id(target.id).pluck(:author_id).uniq
+        User.where(id: author_ids)
+      else
+        note.mentioned_users
+      end
+    recipients = recipients.concat(participants)
 
     # Merge project watchers
     recipients = recipients.concat(project_watchers(note.project)).compact.uniq
 
-    # Reject users with Mention notification level
-    recipients = reject_mention_users(recipients, note.project)
-
-    # Add explicitly mentioned users
-    if target.respond_to?(:participants)
-      recipients = recipients.concat(target.participants)
-    else
-      recipients = recipients.concat(note.mentioned_users)
-    end
+    # Reject users with Mention notification level, except those mentioned in _this_ note.
+    recipients = reject_mention_users(recipients - note.mentioned_users, note.project)
+    recipients = recipients + note.mentioned_users
 
     # Reject mutes users
     recipients = reject_muted_users(recipients, note.project)
@@ -216,18 +219,6 @@ class NotificationService
 
   protected
 
-  def noteable_commenters(note)
-    opts = { noteable_type: note.noteable_type, project_id: note.project_id }
-
-    if note.commit_id.present?
-      opts.merge!(commit_id: note.commit_id)
-    else
-      opts.merge!(noteable_id: note.noteable_id)
-    end
-
-    User.where(id: Note.where(opts).pluck(:author_id))
-  end
-
   # Get project users with WATCH notification level
   def project_watchers(project)
     project_members = project_member_notification(project)