Extend branch support for Static Site Editor

Allow to use both `main` and `master` branches

Changelog: changed

changelogs/unreleased/extend_branch_support_for_sse.yml

+---
+title: Extend branch support for Static Site Editor
+merge_request: 60848
+author:
+type: changed

lib/gitlab/static_site_editor/config/generated_config.rb

@@ -42,11 +42,11 @@ module Gitlab
         end
 
         def supported_content?
-          master_branch? && extension_supported? && file_exists?
+          branch_supported? && extension_supported? && file_exists?
         end
 
-        def master_branch?
-          ref == 'master'
+        def branch_supported?
+          ref.in?(%w[master main])
         end
 
         def extension_supported?

spec/lib/gitlab/static_site_editor/config/generated_config_spec.rb

@@ -54,13 +54,14 @@ RSpec.describe Gitlab::StaticSiteEditor::Config::GeneratedConfig do
           path,
           '',
           message: 'message',
-          branch_name: 'master'
+          branch_name: ref
         )
       end
 
+      let(:ref) { 'main' }
       let(:path) { 'README.md.erb' }
 
-      it { is_expected.to include(is_supported_content: true) }
+      it { is_expected.to include(branch: ref, is_supported_content: true) }
     end
 
     context 'when file path is nested' do
@@ -69,7 +70,7 @@ RSpec.describe Gitlab::StaticSiteEditor::Config::GeneratedConfig do
       it { is_expected.to include(base_url: '/namespace/project/-/sse/master%2Flib%2FREADME.md') }
     end
 
-    context 'when branch is not master' do
+    context 'when branch is not master or main' do
       let(:ref) { 'my-branch' }
 
       it { is_expected.to include(is_supported_content: false) }