Merge branch '6.4' into 7.0

* 6.4:
  [Routing] Document the effect of setting `locale` on a route with locale prefixes

routing.rst

@@ -2072,6 +2072,16 @@ with a locale. This can be done by defining a different prefix for each locale
  ;
  };
 
+.. note::
+
+ If a route being imported includes the special :ref:`_locale <routing-locale-parameter>`
+ parameter in its own definition, Symfony will only import it for that locale
+ and not for the other configured locale prefixes.
+
+ E.g. if a route contains ``locale: 'en'`` in its definition and it's being
+ imported with ``en`` (prefix: empty) and ``nl`` (prefix: ``/nl``) locales,
+ that route will be available only in ``en`` locale and not in ``nl``.
+
 Another common requirement is to host the website on a different domain
 according to the locale. This can be done by defining a different host for each
 locale.