feat: workspace matrix command for detecting affected projects based on diff

lib/src/cli/git_cli.dart

@@ -20,6 +20,30 @@ Make sure the remote exists and you have the correct access rights.''';
 
 /// Git CLI
 class Git {
+  /// Returns file paths changed from [baseRef] to `HEAD`.
+  ///
+  /// Paths are relative to [cwd].
+  static Future<List<String>> changedFiles(
+    String baseRef, {
+    required Logger logger,
+    String cwd = '.',
+  }) async {
+    final result = await _Cmd.run(
+      'git',
+      ['diff', '--name-only', '--relative', '$baseRef...HEAD'],
+      logger: logger,
+      workingDirectory: cwd,
+    );
+
+    final lines = result.stdout
+        .toString()
+        .split(RegExp(r'\r?\n'))
+        .map((line) => line.trim())
+        .where((line) => line.isNotEmpty)
+        .toList();
+    return lines;
+  }
+
   /// Determine whether the [remote] is reachable.
   static Future<void> reachable(Uri remote, {required Logger logger}) async {
     try {

lib/src/command_runner.dart

@@ -38,6 +38,7 @@ class VeryGoodCommandRunner extends CompletionCommandRunner<int> {
     addCommand(TestCommand(logger: _logger));
     addCommand(UpdateCommand(logger: _logger, pubUpdater: pubUpdater));
     addCommand(DartCommand(logger: _logger));
+    addCommand(WorkspaceCommand(logger: _logger));
     addCommand(MCPCommand());
   }
 
@@ -57,6 +58,9 @@ class VeryGoodCommandRunner extends CompletionCommandRunner<int> {
   bool? isWindowsOverride;
   bool get _isWindows => isWindowsOverride ?? Platform.isWindows;
 
+  @override
+  bool get enableAutoInstall => !environment.containsKey('CI');
+
   @override
   void printUsage() => _logger.info(usage);
 

lib/src/commands/commands.dart

@@ -4,3 +4,4 @@ export 'dart/dart.dart';
 export 'packages/packages.dart';
 export 'test/test.dart';
 export 'update.dart';
+export 'workspace/workspace.dart';

lib/src/commands/workspace/commands/commands.dart

@@ -0,0 +1 @@
+export 'matrix.dart';

lib/src/commands/workspace/commands/matrix.dart

@@ -0,0 +1,112 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:args/args.dart';
+import 'package:args/command_runner.dart';
+import 'package:mason/mason.dart';
+import 'package:meta/meta.dart';
+import 'package:universal_io/io.dart';
+import 'package:very_good_cli/src/cli/cli.dart';
+import 'package:very_good_cli/src/workspace_matrix/workspace_matrix.dart';
+
+/// Signature for resolving files changed against a git base ref.
+typedef GitChangedFiles =
+    Future<List<String>> Function({
+      required String baseRef,
+      required String cwd,
+      required Logger logger,
+    });
+
+/// Signature for resolving affected workspace projects.
+typedef ResolveAffectedWorkspaceProjects =
+    List<WorkspaceProject> Function({
+      required Directory rootDirectory,
+      required List<String> changedFiles,
+    });
+
+/// {@template workspace_matrix_command}
+/// `very_good workspace matrix` command.
+/// {@endtemplate}
+class WorkspaceMatrixCommand extends Command<int> {
+  /// {@macro workspace_matrix_command}
+  WorkspaceMatrixCommand({
+    required this.logger,
+    GitChangedFiles? gitChangedFiles,
+    ResolveAffectedWorkspaceProjects? resolveAffectedProjects,
+  }) : _gitChangedFiles = gitChangedFiles ?? _defaultGitChangedFiles,
+       _resolveAffectedProjects =
+           resolveAffectedProjects ?? resolveAffectedWorkspaceProjects {
+    argParser.addOption(
+      'base',
+      help: 'Base git ref used for diffing changes (for example, origin/main).',
+      valueHelp: 'ref',
+    );
+  }
+
+  /// Logger used by this command.
+  final Logger logger;
+  final GitChangedFiles _gitChangedFiles;
+  final ResolveAffectedWorkspaceProjects _resolveAffectedProjects;
+
+  /// [ArgResults] which can be overridden for testing.
+  @visibleForTesting
+  ArgResults? argResultOverrides;
+
+  ArgResults get _argResults => argResultOverrides ?? argResults!;
+
+  @override
+  String get description =>
+      'Return a JSON list of affected projects in the current workspace.';
+
+  @override
+  String get invocation => 'very_good workspace matrix [arguments]';
+
+  @override
+  String get name => 'matrix';
+
+  @override
+  Future<int> run() async {
+    if (_argResults.rest.isNotEmpty) {
+      usageException('This command does not accept positional arguments.');
+    }
+
+    final baseRef = (_argResults['base'] as String?)?.trim();
+    if (baseRef == null || baseRef.isEmpty) {
+      usageException('Missing required option: --base <ref>.');
+    }
+
+    try {
+      final cwd = Directory.current.path;
+      final changedFiles = await _gitChangedFiles(
+        baseRef: baseRef,
+        cwd: cwd,
+        logger: logger,
+      );
+
+      final affectedProjects = _resolveAffectedProjects(
+        rootDirectory: Directory(cwd),
+        changedFiles: changedFiles,
+      );
+
+      logger.info(
+        jsonEncode(
+          affectedProjects.map((project) => project.toJson()).toList(),
+        ),
+      );
+      return ExitCode.success.code;
+    } on UsageException {
+      rethrow;
+    } on Exception catch (error) {
+      logger.err('$error');
+      return ExitCode.unavailable.code;
+    }
+  }
+}
+
+Future<List<String>> _defaultGitChangedFiles({
+  required String baseRef,
+  required String cwd,
+  required Logger logger,
+}) {
+  return Git.changedFiles(baseRef, cwd: cwd, logger: logger);
+}

lib/src/commands/workspace/workspace.dart

@@ -0,0 +1,19 @@
+import 'package:args/command_runner.dart';
+import 'package:mason/mason.dart';
+import 'package:very_good_cli/src/commands/workspace/commands/commands.dart';
+
+/// {@template workspace_command}
+/// `very_good workspace` command for managing Pub workspaces.
+/// {@endtemplate}
+class WorkspaceCommand extends Command<int> {
+  /// {@macro workspace_command}
+  WorkspaceCommand({required Logger logger}) {
+    addSubcommand(WorkspaceMatrixCommand(logger: logger));
+  }
+
+  @override
+  String get description => 'Command for managing Pub workspaces.';
+
+  @override
+  String get name => 'workspace';
+}