contrib/plan9/9mail

packaging: don't use plain 'python' if another python has been specified

Before this change, packaging on CentOS 8 failed because 'python'
is used instead of 'python3'.

Change was tested with:
- make docker-centos7
- make docker-centos8
- make docker-ubuntu-bionic

Differential Revision: https://phab.mercurial-scm.org/D9464

#!/bin/rc
# 9mail - Mercurial email wrapper for upas/marshal

fn usage {
	echo >[1=2] usage: mercurial/9mail -f from to [cc]
	exit usage
}

from=()
cc=()
to=()

switch($1){
case -f
	from=$2
case *
	usage
}

to=($3)
if(~ $#* 4)
	cc=(-C $4)

upasname=$from
upas/marshal $cc $to