OPT_DUP
{ "signer", OPT_DUP, 's', "Signer certificate(s) output file" },
{ "cades", OPT_DUP, '-', "Check signingCertificate (CAdES-BES)" },
OPENSSL_assert(o->retval == OPT_DUP || o->retval > OPT_PARAM);
duplicated = next->retval != OPT_DUP