mda+learn: add --help / -h support

"use Getopt::Long" doesn't seem too slow on a hot page cache,
and it's probably used frequently enough to be in cache.

We'll also start reducing the amount of markup in the .pod and
favoring verbatim text in documentation for readability in
source form, since the bold text seems excessive.

1 files changed, 14 insertions, 4 deletions

diff --git a/script/public-inbox-mda b/script/public-inbox-mda
index 02ca3431..3ed5abb6 100755
--- a/script/public-inbox-mda
+++ b/script/public-inbox-mda
@@ -3,11 +3,21 @@
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 #
 # Mail delivery agent for public-inbox, run from your MTA upon mail delivery
+my $help = <<EOF;
+usage: public-inbox-mda [OPTIONS] </path/to/RFC2822_message
+
+options:
+
+  --no-precheck  skip internal checks for spam messages
+
+See public-inbox-mda(1) man page for full documentation.
+EOF
 use strict;
-use warnings;
-my $usage = 'public-inbox-mda [OPTIONS] < rfc2822_message';
-my $precheck = grep(/\A--no-precheck\z/, @ARGV) ? 0 : 1;
-my ($ems, $emm);
+use Getopt::Long qw(:config gnu_getopt no_ignore_case auto_abbrev);
+my ($ems, $emm, $show_help);
+my $precheck = 1;
+GetOptions('precheck!' => \$precheck, 'help|h' => \$show_help) or
+        do { print STDERR $help; exit 1 };
 
 my $do_exit = sub {
         my ($code) = shift;