SFTP init.

lib/data/model/sftp/absolute_path.dart

@@ -0,0 +1,29 @@
+class AbsolutePath {
+  String path;
+  String? _prePath;
+  AbsolutePath(this.path);
+
+  void update(String newPath) {
+    _prePath = path;
+    if (newPath == '..') {
+      path = path.substring(0, path.lastIndexOf('/'));
+      if (path == '') {
+        path = '/';
+      }
+      return;
+    }
+    if (newPath == '/') {
+      path = '/';
+      return;
+    }
+    path = path + (path.endsWith('/') ? '' : '/') + newPath;
+  }
+
+  bool undo() {
+    if (_prePath == null) {
+      return false;
+    }
+    path = _prePath!;
+    return true;
+  }
+}