Make group navigation controller-driven

appstate/state.go

@@ -597,6 +597,30 @@ func (s *State) MoveSelectedEntry(path []string) error {
 	return nil
 }
 
+func (s *State) DeleteCurrentGroup() error {
+	session, ok := s.Session.(MutableSession)
+	if !ok {
+		return fmt.Errorf("session is not mutable")
+	}
+
+	model, err := session.Current()
+	if err != nil {
+		return err
+	}
+
+	if err := model.DeleteGroup(s.CurrentPath); err != nil {
+		return err
+	}
+
+	session.Replace(model)
+	if len(s.CurrentPath) > 0 {
+		s.CurrentPath = append([]string(nil), s.CurrentPath[:len(s.CurrentPath)-1]...)
+	}
+	s.SelectedEntryID = ""
+	s.Dirty = true
+	return nil
+}
+
 func (s *State) AddAttachmentToSelectedEntry(name string, content []byte) error {
 	session, ok := s.Session.(MutableSession)
 	if !ok {