fix shell options clone for environment

packages/process_run/lib/src/shell_common.dart

@@ -262,7 +262,7 @@ class ShellOptions {
         stdoutEncoding: stdoutEncoding ?? _stdoutEncoding,
         throwOnError: throwOnError ?? _throwOnError,
         workingDirectory: workingDirectory ?? _workingDirectory,
-        environment: shellEnvironment,
+        environment: shellEnvironment ?? _environment,
         noStdoutResult: noStdoutResult ?? _noStdoutResult,
         noStderrResult: noStderrResult ?? _noStderrResult);
   }

packages/process_run/test/shell_environment_test.dart

@@ -319,6 +319,14 @@ void main() {
       shellEnvironment = prevEnv;
     }
   });
+
+  test('cd', () async {
+    var env = ShellEnvironment()..aliases['cd_alias'] = 'cd';
+    var shell = Shell(environment: env);
+    expect(shell.options.environment.aliases['cd_alias'], 'cd');
+    shell = shell.cd('test');
+    expect(shell.options.environment.aliases['cd_alias'], 'cd');
+  });
 }
 
 /// Better with non verbose shell.

packages/process_run/test/shell_options_test.dart

@@ -0,0 +1,18 @@
+@TestOn('vm')
+library;
+
+import 'package:process_run/shell.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('shell_options', () {
+    test('clone', () async {
+      var env = ShellEnvironment()..aliases['clone_alias'] = 'clone';
+      var shellOptions = ShellOptions(environment: env);
+
+      expect(shellOptions.environment.aliases['clone_alias'], 'clone');
+      shellOptions = shellOptions.clone();
+      expect(shellOptions.environment.aliases['clone_alias'], 'clone');
+    });
+  });
+}