Move setup code into its own package

packages/git_setup/lib/loading_error.dart

@@ -0,0 +1,29 @@
+/*
+ * SPDX-FileCopyrightText: 2019-2021 Vishesh Handa <me@vhanda.in>
+ *
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import 'package:flutter/material.dart';
+
+import 'error.dart';
+import 'loading.dart';
+
+class GitHostSetupLoadingErrorPage extends StatelessWidget {
+  final String? errorMessage;
+  final String loadingMessage;
+
+  const GitHostSetupLoadingErrorPage({
+    required this.errorMessage,
+    required this.loadingMessage,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    if (errorMessage == null || errorMessage!.isEmpty) {
+      return GitHostSetupLoadingPage(loadingMessage);
+    }
+
+    return GitHostSetupErrorPage(errorMessage!);
+  }
+}