4 files changed, 34 insertions, 8 deletions
diff --git a/app/services/issuable_base_service.rb b/app/services/issuable_base_service.rb
index 11d2b08bba7..19055fb67ff 100644
--- a/app/services/issuable_base_service.rb
+++ b/app/services/issuable_base_service.rb
@@ -27,6 +27,12 @@ class IssuableBaseService < BaseService
       old_branch, new_branch)
   end
 
+  def create_task_status_note(issuable)
+    issuable.updated_tasks.each do |task|
+      SystemNoteService.change_task_status(issuable, issuable.project, current_user, task)
+    end
+  end
+
   def filter_params(issuable_ability_name = :issue)
     params[:assignee_id]  = "" if params[:assignee_id] == IssuableFinder::NONE
     params[:milestone_id] = "" if params[:milestone_id] == IssuableFinder::NONE
@@ -55,6 +61,7 @@ class IssuableBaseService < BaseService
           old_labels - issuable.labels)
       end
 
+      handle_common_system_notes(issuable)
       handle_changes(issuable)
       issuable.create_new_cross_references!(current_user)
       execute_hooks(issuable, 'update')
@@ -71,4 +78,14 @@ class IssuableBaseService < BaseService
       close_service.new(project, current_user, {}).execute(issuable)
     end
   end
+
+  def handle_common_system_notes(issuable)
+    if issuable.previous_changes.include?('title')
+      create_title_change_note(issuable, issuable.previous_changes['title'].first)
+    end
+
+    if issuable.previous_changes.include?('description') && issuable.tasks?
+      create_task_status_note(issuable)
+    end
+  end
 end
diff --git a/app/services/issues/update_service.rb b/app/services/issues/update_service.rb
index 7c112f731a7..a55a04dd5e0 100644
--- a/app/services/issues/update_service.rb
+++ b/app/services/issues/update_service.rb
@@ -13,10 +13,6 @@ module Issues
         create_assignee_note(issue)
         notification_service.reassigned_issue(issue, current_user)
       end
-
-      if issue.previous_changes.include?('title')
-        create_title_change_note(issue, issue.previous_changes['title'].first)
-      end
     end
 
     def reopen_service
diff --git a/app/services/merge_requests/update_service.rb b/app/services/merge_requests/update_service.rb
index a5db3776eb6..5ff2cc03dda 100644
--- a/app/services/merge_requests/update_service.rb
+++ b/app/services/merge_requests/update_service.rb
@@ -30,10 +30,6 @@ module MergeRequests
         notification_service.reassigned_merge_request(merge_request, current_user)
       end
 
-      if merge_request.previous_changes.include?('title')
-        create_title_change_note(merge_request, merge_request.previous_changes['title'].first)
-      end
-
       if merge_request.previous_changes.include?('target_branch') ||
           merge_request.previous_changes.include?('source_branch')
         merge_request.mark_as_unchecked
diff --git a/app/services/system_note_service.rb b/app/services/system_note_service.rb
index 708c2f00486..7c5d523ef39 100644
--- a/app/services/system_note_service.rb
+++ b/app/services/system_note_service.rb
@@ -341,4 +341,21 @@ class SystemNoteService
 
     "* #{commit_ids} - #{commits_text} from branch `#{branch}`\n"
   end
+
+  # Called when the status of a Task has changed
+  #
+  # noteable  - Noteable object.
+  # project   - Project owning noteable
+  # author    - User performing the change
+  # new_task  - TaskList::Item object.
+  #
+  # Example Note text:
+  #
+  #   "Soandso marked the task Whatever as completed."
+  #
+  # Returns the created Note object
+  def self.change_task_status(noteable, project, author, new_task)
+    body = "Marked the task **#{new_task.source}** as #{new_task.status_label}"
+    create_note(noteable: noteable, project: project, author: author, note: body)
+  end
 end