Re: [PATCH v4] git-send-email: use ! to indicate relative path to command

Gregory Anders [off-list ref] writes:

Presently, the smtpServer config option can use a sendmail-like program

s/Presently, t/T/;  Also if I understand it correctly this is not
just about configuration varible but equally applies to the command
line option --smtp-server, so mention both of them in their full
name, i.e.

    The sendemail.smtpServer configuration variable and the
    "--smtp-server" command line option can name a program to use by
    providing ...

by providing an absolute path to the program as the value for this
option. 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.

Nicely explained.

To that end, this patch allows the smtpServer config option to be
prefixed with a ! character that implements the above behavior; namely,
the specified value (sans the ! character) is used as if the user had
entered it directly on the command line.

	Allow the value of the configuration variable and the
	command line option to be prefixed with a '!' to signal that
	the specified command needs to be looked up on $PATH.

See also https://lore.kernel.org/git/YJrH8uqzapnpNEsb@gpanders.com/ (local).

You summarised the problem description in that message pretty well
in the proposed log message (which is much better than leaving only
a URL and forcing readers to go there), and I suspect there aren't
much readers can learn from by seeing also the article, though.

+	} elsif (file_name_is_absolute($smtp_server) || $smtp_server =~ /^!/) {
+		my $prog = $smtp_server;
+		$prog =~ s/^!//;
+
 		my $pid = open my $sm, '|-';
 		defined $pid or die $!;
 		if (!$pid) {
-			exec($smtp_server, @sendmail_parameters) or die $!;
+			exec($prog, @sendmail_parameters) or die $!;
 		}

Looking good.

Thanks.