Add system note when user approves merge request

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/controllers/projects/merge_requests_controller.rb

@@ -200,7 +200,10 @@ class Projects::MergeRequestsController < Projects::ApplicationController
   def approve
     @approval = @merge_request.approvals.new
     @approval.user = current_user
-    @approval.save
+
+    if @approval.save
+      SystemNoteService.approve_mr(@merge_request, current_user)
+    end
 
     redirect_to merge_request_path(@merge_request)
   end

app/services/system_note_service.rb

@@ -255,6 +255,22 @@ class SystemNoteService
     notes.count > 0
   end
 
+  # Called when the merge request is approved by user
+  #
+  # noteable - Noteable object
+  # user     - User performing approve
+  #
+  # Example Note text:
+  #
+  #   "Approved by @rspeicher"
+  #
+  # Returns the created Note object
+  def self.approve_mr(noteable, user)
+    body = "Approved by @#{user.username}"
+
+    create_note(noteable: noteable, project: noteable.project, author: user, note: body)
+  end
+
   private
 
   def self.create_note(args = {})

spec/services/system_note_service_spec.rb

@@ -442,4 +442,17 @@ describe SystemNoteService do
       end
     end
   end
+
+  describe '.approve_mr' do
+    let(:noteable)    { create(:merge_request, source_project: project) }
+    subject { described_class.approve_mr(noteable, author) }
+
+    it_behaves_like 'a system note'
+
+    context 'when assignee added' do
+      it 'sets the note text' do
+        expect(subject.note).to eq "Approved by @#{author.username}"
+      end
+    end
+  end
 end