static S platformQuoteOpt(S s) {
  ret empty(s) || containsUnsafePlatformCmdLineChar(s) ? platformQuote(s) : s;
}

static S platformQuoteOpt(File f) {
  ret platformQuoteOpt(f2s(f));
}

sS platformQuoteOpt(O o) {
  if (o cast File) ret platformQuoteOpt(o);
  ret platformQuoteOpt(strOrEmpty(o));
}