AutoDevOps banner hidden on explicit CI config

Extends the helper method to no show the banner as soon as the project
has a `.gitlab-ci.yml` file on the default branch.

Fixes gitlab-org/gitlab-ce#37652

app/helpers/auto_devops_helper.rb

@@ -3,6 +3,8 @@ module AutoDevopsHelper
     Feature.get(:auto_devops_banner_disabled).off? &&
       show_callout?('auto_devops_settings_dismissed') &&
       can?(current_user, :admin_pipeline, project) &&
-      project.has_auto_devops_implicitly_disabled?
+      project.has_auto_devops_implicitly_disabled? &&
+      !project.repository.gitlab_ci_yml &&
+      project.ci_services.active.none?
   end
 end

changelogs/unreleased/zj-auto-devops-banner.yml

@@ -0,0 +1,6 @@
+---
+title: Do not show the Auto DevOps banner when the project has a .gitlab-ci.yml on
+  master
+merge_request:
+author:
+type: fixed

spec/helpers/auto_devops_helper_spec.rb

@@ -65,5 +65,21 @@ describe AutoDevopsHelper do
 
       it { is_expected.to eq(false) }
     end
+
+    context 'when master contains a .gitlab-ci.yml file' do
+      before do
+        allow(project.repository).to receive(:gitlab_ci_yml).and_return("script: [ 'test']")
+      end
+
+      it { is_expected.to eq(false) }
+    end
+
+    context 'when another service is enabled' do
+      before do
+        create(:service, project: project, category: :ci, active: true)
+      end
+
+      it { is_expected.to eq(false) }
+    end
   end
 end