provide default implementation of IFile::reloadBehavior()

there only two classes of files anyway: regularly editable ones which may
ask for interaction, and "background" files which always operate silently.
the regular case is the more complex one, so put that into the base class.

src/plugins/coreplugin/ifile.cpp

@@ -42,6 +42,15 @@ IFile::~IFile()
 {
 }
 
+IFile::ReloadBehavior IFile::reloadBehavior(ChangeTrigger state, ChangeType type) const
+{
+    if (type == TypePermissions)
+        return BehaviorSilent;
+    if (type == TypeContents && state == TriggerInternal && !isModified())
+        return BehaviorSilent;
+    return BehaviorAsk;
+}
+
 void IFile::checkPermissions()
 {
 }