Then -m switch was used only for the key import and export, but for some time, it can be also used for key generation. This is important mostly after the key format change to OpenSSH when one needs a interoperability with tools not supporting this format. * Add the -m to the first synopsis line: ssh-keygen [-q] [-m key_format] [-b bits] [-t dsa | ecdsa | ed25519 | rsa] [-N new_passphrase] [-C comment] [-f output_keyfile] * Change the description of the -m option to Specify a key format for the -i (import), -e (export) conversion options or -m (key generation) option.
The -m switch is also accepted for the passphrase change of ssh-keygen, which is not documented either. With the light of the new OpenSSH key format by default, the manual page for the ssh-keygen should be updated with some simple hint how to convert PEM to OpenSSH and back, since this is pretty common requirement, but the manual page is not helpful in this way -- the -i nor -e do not work and only way I found that worked for me was changing passphrase to convert to new key format (or old one).
I've committed some manpage tweaks for these
closing resolved bugs as of 8.6p1 release