Allow creating default branch in snippet repositories

changelogs/unreleased/fj-allow-create-snippet-default-branch.yml

+---
+title: Allow creating default branch in snippet repositories
+merge_request: 26294
+author:
+type: fixed

lib/gitlab/checks/snippet_check.rb

@@ -3,6 +3,7 @@
 module Gitlab
   module Checks
     class SnippetCheck < BaseChecker
+      DEFAULT_BRANCH = 'master'.freeze
       ERROR_MESSAGES = {
         create_delete_branch: 'You can not create or delete branches.'
       }.freeze
@@ -29,6 +30,12 @@ module Gitlab
 
         true
       end
+
+      private
+
+      def creation?
+        @branch_name != DEFAULT_BRANCH && super
+      end
     end
   end
 end

spec/lib/gitlab/checks/snippet_check_spec.rb

@@ -25,10 +25,19 @@ describe Gitlab::Checks::SnippetCheck do
 
     context 'trying to create the branch' do
       let(:oldrev) { '0000000000000000000000000000000000000000' }
+      let(:ref) { 'refs/heads/feature' }
 
       it 'raises an error' do
         expect { subject.exec }.to raise_error(Gitlab::GitAccess::ForbiddenError, 'You can not create or delete branches.')
       end
+
+      context "when branch is 'master'" do
+        let(:ref) { 'refs/heads/master' }
+
+        it "allows the operation" do
+          expect { subject.exec }.not_to raise_error
+        end
+      end
     end
   end
 end