// should work in all cases, except if the other program is running; then
// it won't see the changes until it restarts
static void addToOtherProgramsPersistentHashMap(S progID, S persistenceName, O key, O value) {
  File f = persistentMapLogFile(progID, persistenceName);
  logStructure_twoFiles(
    f, fileAppendToName(f, ".bak"), ll(key, value));
}