Group name validation only on group name update

This is to prevent untended consequence
of validating name, even if it was not updated.

app/models/group.rb

@@ -72,7 +72,7 @@ class Group < Namespace
   validates :two_factor_grace_period, presence: true, numericality: { greater_than_or_equal_to: 0 }
   validates :name,
     format: { with: Gitlab::Regex.group_name_regex,
-              message: Gitlab::Regex.group_name_regex_message }
+              message: Gitlab::Regex.group_name_regex_message }, if: :name_changed?
 
   add_authentication_token_field :runners_token, encrypted: -> { Feature.enabled?(:groups_tokens_optional_encryption, default_enabled: true) ? :optional : :required }
 

ee/spec/controllers/subscriptions_controller_spec.rb

@@ -202,7 +202,18 @@ describe SubscriptionsController do
           group.save
           subject
 
-          expect(response.body).to include({ name: ["can't be blank", Gitlab::Regex.group_name_regex_message] }.to_json)
+          expect(response.body).to include({ name: ["can't be blank"] }.to_json)
+        end
+
+        context 'when invalid name is passed' do
+          let(:group) { Group.new(path: 'foo', name: '<script>alert("attack")</script>') }
+
+          it 'returns the errors in json format' do
+            group.save
+            subject
+
+            expect(response.body).to include({ name: [Gitlab::Regex.group_name_regex_message] }.to_json)
+          end
         end
       end