Don't auto-set MR title for confidential issues

app/services/merge_requests/build_service.rb

@@ -68,7 +68,7 @@ module MergeRequests
         commit = commits.first
         merge_request.title       = commit.title
         merge_request.description ||= commit.description.try(:strip)
-      elsif iid && (issue = merge_request.target_project.get_issue(iid))
+      elsif iid && (issue = merge_request.target_project.get_issue(iid)) && !issue.try(:confidential?)
         case issue
         when Issue
           merge_request.title = "Resolve \"#{issue.title}\""

spec/services/merge_requests/build_service_spec.rb

@@ -5,7 +5,8 @@ describe MergeRequests::BuildService, services: true do
 
   let(:project) { create(:project) }
   let(:user) { create(:user) }
-  let(:issue) { create(:issue, project: project, title: 'A bug') }
+  let(:issue_confidential) { false }
+  let(:issue) { create(:issue, project: project, title: 'A bug', confidential: issue_confidential) }
   let(:description) { nil }
   let(:source_branch) { 'feature-branch' }
   let(:target_branch) { 'master' }
@@ -156,6 +157,14 @@ describe MergeRequests::BuildService, services: true do
             expect(merge_request.title).to eq("#{issue.iid.succ} fix issue")
           end
         end
+
+        context 'issue is confidential' do
+          let(:issue_confidential) { true }
+
+          it 'uses the title of the branch as the merge request title' do
+            expect(merge_request.title).to eq("#{issue.iid} fix issue")
+          end
+        end
       end
 
       context 'branch starts with external issue IID followed by a hyphen' do