Implement diff on close, on revert and on external modification

Task-number: QTCREATORBUG-1531
Change-Id: I8c9a740d66eb7836b3df6850ac243260fd282b32
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/coreplugin/diffservice.h

@@ -0,0 +1,47 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 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 "core_global.h"
+#include <QObject>
+
+QT_FORWARD_DECLARE_CLASS(QStringList)
+
+namespace Core {
+
+class CORE_EXPORT DiffService
+{
+public:
+    virtual ~DiffService() {}
+
+    virtual void diffModifiedFiles(const QStringList &fileNames) = 0;
+};
+
+} // namespace Core
+
+QT_BEGIN_NAMESPACE
+Q_DECLARE_INTERFACE(Core::DiffService, "Core::DiffService")
+QT_END_NAMESPACE