Re: [PATCH v2 1/1] send-email: add client certificate options

> For SMTP servers that do "mutual certificate verification", the mail
> client is required to present its own TLS certificate as well. This
> patch adds --smtp-ssl-client-cert and --smtp-ssl-client-key for such
> servers.
>
> The problem of which private key for the certificate is chosen arises
> when there are private keys in both the certificate and private key
> file. According to the documentation of IO::Socket::SSL(link supplied),
> the behaviour(the private key chosen) depends on the format of the
> certificate. In a nutshell,
>
> 	- PKCS12: the key in the cert always takes the precedence
> 	- PEM: if the key file is not given, it will "try" to read one
> 	  from the cert PEM file
>
> Many users may find this discrepancy unintuitive.
>
> In terms of client certificate, git-send-email is implemented in a way
> that what's possible with perl's SSL library is exposed to the user as
> much as possible. In this instance, the user may choose to use a PEM
> file that contains both certificate and private key should be
> at their discretion despite the implications.
>
> Link: https://metacpan.org/pod/IO::Socket::SSL#SSL_cert_file-%7C-SSL_cert-%7C-SSL_key_file-%7C-SSL_key
> Link: https://lore.kernel.org/all/319bf98c-52df-4bf9-b157-e4bc2bf087d6@dev.snart.me/
>
> Signed-off-by: David Timber <dxdt@dev.snart.me>
> ---
>  Documentation/config/sendemail.adoc | 16 ++++++++++
>  Documentation/git-send-email.adoc   | 19 ++++++++++++
>  git-send-email.perl                 | 47 ++++++++++++++++++++++-------
>  3 files changed, 71 insertions(+), 11 deletions(-)