Allow the default branch as branch name

changelogs/unreleased-ee/bvl-allow-default-branch-as-branch-name.yml

+---
+title: Always allow the default branch as a branch name
+merge_request: 3154
+author:
+type: fixed

lib/gitlab/checks/change_access.rb

@@ -185,6 +185,7 @@ module Gitlab
       def branch_name_allowed_by_push_rule?(push_rule)
         return true unless push_rule
         return true if @branch_name.blank?
+        return true if @branch_name == @project.default_branch
 
         push_rule.branch_name_allowed?(@branch_name)
       end

spec/lib/gitlab/checks/change_access_spec.rb

@@ -266,6 +266,15 @@ describe Gitlab::Checks::ChangeAccess do
             expect { subject }.to raise_error(Gitlab::GitAccess::UnauthorizedError, "Branch name does not follow the pattern '^(w*)$'")
           end
         end
+
+        context 'when the default branch does not match the push rules' do
+          let(:push_rule) { create(:push_rule, branch_name_regex: 'not-master') }
+          let(:ref) { "refs/heads/#{project.default_branch}" }
+
+          it 'allows the default branch even if it does not match push rule' do
+            expect { subject }.not_to raise_error
+          end
+        end
       end
 
       context 'existing member rules' do