Add update_versions.dart script to update package versions in pubspec.yaml files under packages/ directory.

tool/update_versions.dart

@@ -0,0 +1,78 @@
+import 'dart:io';
+
+/// Usage examples:
+///   dart run tool/update_versions.dart -- version=1.2.3
+///   melos run set-version -- version=1.2.3
+void main(List<String> args) {
+  final versionArg = args.firstWhere(
+    (a) => a.startsWith('version='),
+    orElse: () => 'version=',
+  );
+  final version = versionArg.split('=', 2).last.trim();
+  if (version.isEmpty) {
+    stderr.writeln('Usage: dart run tool/update_versions.dart -- version=<semver>');
+    exit(64);
+  }
+
+  final packagesDir = Directory('packages');
+  if (!packagesDir.existsSync()) {
+    stderr.writeln("No 'packages' directory found at repo root.");
+    exit(1);
+  }
+
+  final pubspecFiles = packagesDir
+      .listSync(recursive: false)
+      .whereType<Directory>()
+      .map((d) => File('${d.path}\\pubspec.yaml'))
+      .where((f) => f.existsSync())
+      .toList()
+    ..sort((a, b) => a.path.compareTo(b.path));
+
+  if (pubspecFiles.isEmpty) {
+    stderr.writeln('No pubspec.yaml files found in packages/*');
+    exit(1);
+  }
+
+  int updated = 0;
+  final updatedPkgs = <String>[];
+  for (final file in pubspecFiles) {
+    final content = file.readAsStringSync();
+
+    // Skip if it's clearly an app (heuristic): has 'flutter:' and 'uses-material-design:' at top-level
+    // but the requirement is to update all packages under packages/*. We will proceed regardless.
+
+    final nameMatch = RegExp(r'^name:\s*(.+)$', multiLine: true).firstMatch(content);
+    final pkgName = nameMatch != null ? nameMatch.group(1)!.trim() : file.parent.path.split('\\').last;
+
+    String updatedContent;
+    final versionRe = RegExp(r'^version:\s*.*$', multiLine: true);
+    if (versionRe.hasMatch(content)) {
+      updatedContent = content.replaceFirstMapped(versionRe, (_) => 'version: $version');
+    } else {
+      // Insert after description if present, otherwise after name.
+      final descRe = RegExp(r'^(description:.*)$', multiLine: true);
+      if (descRe.hasMatch(content)) {
+        updatedContent = content.replaceFirstMapped(descRe, (m) => '${m.group(1)}\nversion: $version');
+      } else {
+        final nameRe = RegExp(r'^(name:.*)$', multiLine: true);
+        if (nameRe.hasMatch(content)) {
+          updatedContent = content.replaceFirstMapped(nameRe, (m) => '${m.group(1)}\nversion: $version');
+        } else {
+          // If neither present, prepend version at top.
+          updatedContent = 'version: $version\n$content';
+        }
+      }
+    }
+
+    if (updatedContent != content) {
+      file.writeAsStringSync(updatedContent);
+      updated++;
+      updatedPkgs.add(pkgName);
+    }
+  }
+
+  stdout.writeln('Updated version to $version in $updated package(s).');
+  for (final p in updatedPkgs) {
+    stdout.writeln(' - $p');
+  }
+}