Merge branch '27456-improve-feedback-when-dev-cannot-push-to-empty-repo' into 'master'

Improve feedback when a developer cannot push in an empty repository

Closes #27456

See merge request gitlab-org/gitlab-ce!20519

changelogs/unreleased/27456-improve-feedback-when-dev-cannot-push-to-empty-repo.yml

+---
+title: Improve feedback when a developer is unable to push to an empty repository
+merge_request: 20519
+author:
+type: changed

lib/gitlab/checks/change_access.rb

@@ -93,7 +93,7 @@ module Gitlab
           end
         else
           unless user_access.can_push_to_branch?(branch_name)
-            raise GitAccess::UnauthorizedError, ERROR_MESSAGES[:push_protected_branch]
+            raise GitAccess::UnauthorizedError, push_to_protected_branch_rejected_message
           end
         end
       end
@@ -140,6 +140,29 @@ module Gitlab
 
       private
 
+      def push_to_protected_branch_rejected_message
+        if project.empty_repo?
+          empty_project_push_message
+        else
+          ERROR_MESSAGES[:push_protected_branch]
+        end
+      end
+
+      def empty_project_push_message
+        <<~MESSAGE
+
+        A default branch (e.g. master) does not yet exist for #{project.full_path}
+        Ask a project Owner or Maintainer to create a default branch:
+
+          #{project_members_url}
+
+        MESSAGE
+      end
+
+      def project_members_url
+        Gitlab::Routing.url_helpers.project_project_members_url(project)
+      end
+
       def should_run_commit_validations?
         commit_check.validate_lfs_file_locks?
       end

spec/lib/gitlab/checks/change_access_spec.rb

@@ -132,6 +132,16 @@ describe Gitlab::Checks::ChangeAccess do
           expect { subject.exec }.to raise_error(Gitlab::GitAccess::UnauthorizedError, 'You are not allowed to push code to protected branches on this project.')
         end
 
+        context 'when project repository is empty' do
+          let(:project) { create(:project) }
+
+          it 'raises an error if the user is not allowed to push to protected branches' do
+            expect(user_access).to receive(:can_push_to_branch?).and_return(false)
+
+            expect { subject.exec }.to raise_error(Gitlab::GitAccess::UnauthorizedError, /Ask a project Owner or Maintainer to create a default branch/)
+          end
+        end
+
         context 'branch deletion' do
           let(:newrev) { '0000000000000000000000000000000000000000' }
           let(:ref) { 'refs/heads/feature' }