On 2021-05-11 at 23:49:35, Gregory Anders wrote:
> The sendemail.smtpServer configuration option and the '--smtp-server'
> command line option can name a program to use by providing an absolute
> path to the program. However, an absolute path is not always portable
> and it is often preferable to simply specify a program name and have
> 'git-send-email' find that program on $PATH.
> 
> For example, if a user wishes to use msmtp to send emails, they might
> be able to simply use
> 
>     [sendemail]
>             smtpServer = !msmtp
> 
> instead of using the full path. This is particularly useful when a
> common git config file is used across multiple systems where the
> absolute path to a given program may differ.
> 
> To that end, this patch allows both the configuration and command line
> options to be prefixed with a '!' character to indicate that the
> specified command should be found on $PATH, as if the user had entered
> it directly on the command line.

I think the idea of providing a way to invoke a sendmail-compatible mail
server is a good idea.

> Signed-off-by: Gregory Anders <greg@gpanders.com>
> ---
> Diff from v4:
> 
> * Update the test with suggestions from Jeff King (this should fix 
>   erroneous test failures caused by patch files being deleted by earlier 
>   tests)
> * Reword the commit message with feedback from Jeff King and Junio 
>   Hamano
> 
>  Documentation/git-send-email.txt | 13 +++++++------
>  git-send-email.perl              |  7 +++++--
>  t/t9001-send-email.sh            | 12 ++++++++++++
>  3 files changed, 24 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/git-send-email.txt b/Documentation/git-send-email.txt
> index 93708aefea..418e66c703 100644
> --- a/Documentation/git-send-email.txt
> +++ b/Documentation/git-send-email.txt
> @@ -212,12 +212,13 @@ a password is obtained using 'git-credential'.
>  --smtp-server=<host>::
>  	If set, specifies the outgoing SMTP server to use (e.g.
>  	`smtp.example.com` or a raw IP address).  Alternatively it can
> -	specify a full pathname of a sendmail-like program instead;
> -	the program must support the `-i` option.  Default value can
> -	be specified by the `sendemail.smtpServer` configuration
> -	option; the built-in default is to search for `sendmail` in
> -	`/usr/sbin`, `/usr/lib` and $PATH if such program is
> -	available, falling back to `localhost` otherwise.
> +	specify a sendmail-like program instead, either by a full
> +	path-name or by prefixing the program name with `!`.  The
> +	program must support the `-i` option.  Default value can be
> +	specified by the `sendemail.smtpServer` configuration option;
> +	the built-in default is to search for `sendmail` in `/usr/sbin`,
> +	`/usr/lib` and $PATH if such program is available, falling back
> +	to `localhost` otherwise.

Elsewhere we use the ! syntax we invoke the shell, and I would suggest
that we do the same here.  That means we'll get PATH functionality by
default and we'll let people do a modicum of scripting if they like.
-- 
brian m. carlson (he/him or they/them)
Houston, Texas, US