ClangCodeModel: Force clangd restart on external changes

Neither we nor clangd can afford to watch all source files, which means
that after e.g. a branch switch we can easily end up in an inconsistent
state.
We alleviate this problem by restarting clangd if at least one open file
was changed externally.

Change-Id: I7e0d14835e3afbd7a64c3233614f2161282dddc0
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/texteditor/textdocument.cpp

@@ -106,6 +106,7 @@ public:
     QScopedPointer<Formatter> m_formatter;
 
     int m_autoSaveRevision = -1;
+    bool m_silentReload = false;
 
     TextMarks m_marksCache; // Marks not owned
     Utils::Guard m_modificationChangedGuard;
@@ -426,6 +427,13 @@ QAction *TextDocument::createDiffAgainstCurrentFileAction(
     return diffAction;
 }
 
+#ifdef WITH_TESTS
+void TextDocument::setSilentReload()
+{
+    d->m_silentReload = true;
+}
+#endif
+
 void TextDocument::triggerPendingUpdates()
 {
     if (d->m_fontSettingsNeedsApply)
@@ -707,6 +715,13 @@ void TextDocument::setFilePath(const Utils::FilePath &newName)
     IDocument::setFilePath(newName.absoluteFilePath());
 }
 
+IDocument::ReloadBehavior TextDocument::reloadBehavior(ChangeTrigger state, ChangeType type) const
+{
+    if (d->m_silentReload)
+        return IDocument::BehaviorSilent;
+    return BaseTextDocument::reloadBehavior(state, type);
+}
+
 bool TextDocument::isModified() const
 {
     return d->m_document.isModified();