Docs: include gpg's --armor option on export

[alastairs]

I found that a GPG exported with solely --export-secret-keys could not be imported via gpg --import, even on the same machine and with the same GPG version as those from which the key was exported. Including the --armor option, however, producing ASCII-armoured output, resolved the issue.

[hiddeco]

Can you provide some details about e.g. the GnuPG version you are running? As on my machine I am perfectly able to perform the actions mentioned without the --armor option:

$ gpg --export-secret-keys 0x36BFC7F119A1C9F1 > secret.key
$ export GNUPGHOME=$(mktemp -d); echo $GNUPGHOME
/tmp/tmp.y8yrt27Qux
$ gpg --import secret.key
gpg: keybox '/tmp/tmp.y8yrt27Qux/pubring.kbx' created
gpg: /tmp/tmp.y8yrt27Qux/trustdb.gpg: trustdb created
gpg: key 36BFC7F119A1C9F1: public key "Flux <support@weave.works>" imported
gpg: key 36BFC7F119A1C9F1: secret key imported
gpg: Total number processed: 1
gpg:               imported: 1
gpg:       secret keys read: 1
gpg:   secret keys imported: 1
$  gpg --version
gpg (GnuPG) 2.2.18
libgcrypt 1.8.5
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Home: /tmp/tmp.y8yrt27Qux
Supported algorithms:
Pubkey: RSA, ELG, DSA, ECDH, ECDSA, EDDSA
Cipher: IDEA, 3DES, CAST5, BLOWFISH, AES, AES192, AES256, TWOFISH,
        CAMELLIA128, CAMELLIA192, CAMELLIA256
Hash: SHA1, RIPEMD160, SHA256, SHA384, SHA512, SHA224
Compression: Uncompressed, ZIP, ZLIB, BZIP2

[alastairs]

Sure thing. I'm running on Windows, with GPG installed via scoop. I have the same version as you.

> gpg --export-secret-keys F8FB0DAE2EA9AD9156F0DB1912AC019F3F154890 > secret.key
> gpg --import .\secret.key
gpg: packet(3) with unknown version 7
gpg: read_block: read error: Invalid packet
gpg: import from '.\secret.key' failed: Invalid keyring
gpg: Total number processed: 0

The same thing happens if I set GNUPGHOME as you did.

> gpg --version
gpg (GnuPG) 2.2.18
libgcrypt 1.8.5
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Home: C:/Users/AlastairSmith/scoop/apps/gpg/current/home
Supported algorithms:
Pubkey: RSA, ELG, DSA, ECDH, ECDSA, EDDSA
Cipher: IDEA, 3DES, CAST5, BLOWFISH, AES, AES192, AES256, TWOFISH,
CAMELLIA128, CAMELLIA192, CAMELLIA256
Hash: SHA1, RIPEMD160, SHA256, SHA384, SHA512, SHA224
Compression: Uncompressed, ZIP, ZLIB, BZIP2

[hiddeco]

Seems to be related to https://dev.gnupg.org/T3194. Given the dos2unix solution mentioned there is a pain to both document and use, adding the --armor option makes sense.