ClangFormat: Rework clangformatconfigwidget

- Move logic work with clang-format file to
additional class to make clangformatconfigwidget
responsible only for work with ui elements.
- Fix functionality: when new BasedOnStyle was
chosen all fields were empty or set in default,
now it fills with the corresponding value.

Change-Id: I2ee42a502e87da761274d293a7f0a38fda98804d
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/clangformat/clangformatfile.h

@@ -0,0 +1,60 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#pragma once
+
+#include "utils/filepath.h"
+#include <clang/Format/Format.h>
+
+namespace ClangFormat {
+
+class ClangFormatFile
+{
+public:
+    explicit ClangFormatFile(Utils::FilePath file);
+    clang::format::FormatStyle format();
+
+    Utils::FilePath filePath();
+    void resetStyleToLLVM();
+    void setBasedOnStyle(QString styleName);
+    void setStyle(clang::format::FormatStyle style);
+    QString setStyle(QString style);
+    void clearBasedOnStyle();
+
+    using Field = std::pair<QString, QString>;
+    QString changeFields(QList<Field> fields);
+    QString changeField(Field field);
+
+private:
+    void saveNewFormat();
+    void saveNewFormat(QByteArray style);
+
+private:
+    Utils::FilePath m_filePath;
+    clang::format::FormatStyle m_style;
+};
+
+
+} // namespace ClangFormat