* src/gpgme.h.in (GPGME_SIG_MODE_ARCHIVE): New signature mode.
* src/engine-gpg.c (append_args_from_sender,
append_args_from_sig_notations): Use add_gpg_arg_with_value
for gpg-only options with a value.
(gpg_sign): Set use_gpgtar engine flag if GPGME_SIG_MODE_ARCHIVE mode
is set. Check for new enough gpg. Use add_gpg_arg_with_value for
gpg-only options with a value and add_gpg_arg for gpg-only options
without a value. Set extra options for gpgtar and pass input data to
stdin when using gpgtar.
* src/sign.c (sign_start): Add GPGME_SIG_MODE_ARCHIVE as valid mode.
* tests/run-sign.c (show_usage): New options --archive and
--diagnostics.
(main): Parse new options. Sign with gpgtar if --archive is given.
Print stderr of gpg/gpgtar if --diagnostics is given.