Show progress indicator while reloading diff

Change-Id: Ieefdb885682f01e0e1c8cec90f4769e832650a0c
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/diffeditor/diffeditordocument.cpp

@@ -328,6 +328,7 @@ QString DiffEditorDocument::plainText() const
 void DiffEditorDocument::beginReload()
 {
     emit aboutToReload();
+    m_isReloading = true;
     const bool blocked = blockSignals(true);
     setDiffFiles(QList<FileData>(), QString());
     setDescription(QString());
@@ -336,6 +337,7 @@ void DiffEditorDocument::beginReload()
 
 void DiffEditorDocument::endReload(bool success)
 {
+    m_isReloading = false;
     emit reloadFinished(success);
 }