config: Support setting sideload-repos option

app/flatpak-builtins-config.c

@@ -199,6 +199,18 @@ get_lang_default (FlatpakDir *dir)
   return g_strjoinv (";", langs);
 }
 
+static char *
+parse_string (const char *value, GError **error)
+{
+  return g_strdup (value);
+}
+
+static char *
+print_string (const char *value)
+{
+  return g_strdup (value);
+}
+
 typedef struct
 {
   const char *name;
@@ -210,6 +222,7 @@ typedef struct
 ConfigKey keys[] = {
   { "languages", parse_lang, print_lang, get_lang_default },
   { "extra-languages", parse_locale, print_locale, NULL },
+  { "sideload-repos", parse_string, print_string, NULL },
 };
 
 static ConfigKey *

system-helper/flatpak-system-helper.c

@@ -1138,7 +1138,9 @@ handle_configure (FlatpakSystemHelper   *object,
       return TRUE;
     }
 
-  if ((strcmp (arg_key, "languages") != 0) && (strcmp (arg_key, "extra-languages") != 0))
+  if ((strcmp (arg_key, "languages") != 0) &&
+      (strcmp (arg_key, "extra-languages") != 0) &&
+      (strcmp (arg_key, "sideload-repos") != 0))
     {
       g_dbus_method_invocation_return_error (invocation, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS,
                                              "Unsupported key: %s", arg_key);