patchsend-email: improve recipients_cmd()

> We don't need to quote the filename to pass to the command, we can use
> an array of all the arguments to pass to the command, which is safer,
> and more extensible.
>
> Commit a47eab0 (send-email: use the three-arg form of open in
> recipients_cmd) stated we couldn't pass $file directly, but in fact, we
> can, the multi-word string is passed as is, and we can pass an array
> too.

> Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
> ---
>  git-send-email.perl | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/git-send-email.perl b/git-send-email.perl
> index bd13cc8..7880d12 100755
> --- a/git-send-email.perl
> +++ b/git-send-email.perl
> @@ -1452,11 +1452,11 @@ foreach my $t (@files) {
>  # Execute a command (e.g. $to_cmd) to get a list of email addresses
>  # and return a results array
>  sub recipients_cmd {
> -	my ($prefix, $what, $cmd, $file) = @_;
> +	my ($prefix, $what, $cmd, @args) = @_;
>  
>  	my $sanitized_sender = sanitize_address($sender);
>  	my @addresses = ();
> -	open my $fh, "-|", "$cmd \Q$file\E"
> +	open my $fh, "-|", $cmd, @args
>  	    or die "($prefix) Could not execute '$cmd'";
>  	while (my $address = <$fh>) {
>  		$address =~ s/^\s*//g;

> Felipe Contreras <felipe.contreras@gmail.com> writes:
>
>> We don't need to quote the filename to pass to the command, we can use
>> an array of all the arguments to pass to the command, which is safer,
>> and more extensible.
>>
>> Commit a47eab0 (send-email: use the three-arg form of open in
>> recipients_cmd) stated we couldn't pass $file directly, but in fact, we
>> can, the multi-word string is passed as is, and we can pass an array
>> too.
>
> I think the comment is not about passing $file directly, but is
> about passing $cmd that could be multi-word string directly.  The
> caller expects it be split into command and its earlier part of
> command line parameters, so that you can say
>
>     $cmd = "cccmd --frotz --nitfol"

> Felipe Contreras <felipe.contreras@gmail.com> writes:
>
>>>         open $fh, "-|", qw(sh -c), $cmd, @args
>>
>> That doesn't seem to work for me.
>
> My fault.  It needs to form a command line like this:
>
>         sh -c 'cccmd --frotz --nitfol "$@"' - a r g s
>
> [jc: goes and tries
>         $ sh -c 'echo X Y "$@"' - a r g s
>         X Y a r g s
> ]
>
> so if we want to get rid of \Q\E, it would be:
>
>         open $fh, '-|', qw(sh -c), "$cmd " . '"$@"', '-', @args
>

>> so if we want to get rid of \Q\E, it would be:
>>
>>         open $fh, '-|', qw(sh -c), "$cmd " . '"$@"', '-', @args
>>
>
> I don't know if that would be better, or converting @args to a list of
> quoted strings, essentially keeping the current behavior.