make copy work, also some abstraction and new provider

lib/providers/sftp_provider.dart

@@ -0,0 +1,41 @@
+import 'package:dartssh2/dartssh2.dart';
+import 'package:flutter/material.dart';
+import 'package:fluxcloud/sftp_worker.dart';
+
+class SftpProvider extends ChangeNotifier {
+  final SftpWorker _sftpWorker;
+
+  String _path = '/';
+  bool _isLoading = false;
+  late List<SftpName> _dirContents;
+
+  SftpProvider(this._sftpWorker) {
+    listDir();
+  }
+
+  SftpWorker get sftpWorker => _sftpWorker;
+
+  String get path => _path;
+  bool get isLoading => _isLoading;
+  List<SftpName> get dirContents  => _dirContents;
+
+  Future<void> listDir() async {
+    _isLoading = true;
+    notifyListeners();
+    _dirContents =  await _sftpWorker.listdir(_path);
+    _isLoading = false;
+    notifyListeners();
+  }
+
+  void goToPrevDir() {
+    _path = _path.substring(0, _path.length - 1);
+    _path = _path.substring(0, _path.lastIndexOf('/')+1);
+    listDir();
+  }
+
+  void goToDir(String path) {
+    _path = path;
+    listDir();
+  }
+
+}