mbox_reader: do not blindly pass --rsyncable to gzip

FreeBSD gzip does not support --rsyncable, though my VM
usually has pigz installed.

diff --git a/lib/PublicInbox/MboxReader.pm b/lib/PublicInbox/MboxReader.pm
index 5a754cb8f57ad07de73d1341207bfa901b0a1dcc..beffabe8e55c3160a14afb74dfc3b3276c7a94cc 100644 (file)
--- a/lib/PublicInbox/MboxReader.pm
+++ b/lib/PublicInbox/MboxReader.pm
@@ -144,7 +144,7 @@ sub reads {
 # { foo => '' } means "--foo" is passed to the command-line,
 # otherwise { foo => '--bar' } passes "--bar"
 my %zsfx2cmd = (
-       gz => [ qw(GZIP pigz gzip), { rsyncable => '' } ],
+       gz => [ qw(GZIP pigz gzip) ],
        bz2 => [ 'bzip2', {} ],
        xz => [ 'xz', {} ],
        # don't add new entries here unless MUA support is widely available
@@ -160,7 +160,7 @@ sub zsfx2cmd ($$$) {
        my ($zsfx, $decompress, $lei) = @_;
        my $x = $zsfx2cmd{$zsfx} // die "BUG: no support for suffix=.$zsfx";
        my @info = @$x;
-       my $cmd_opt = pop @info;
+       my $cmd_opt = ref($info[-1]) ? pop(@info) : undef;
        my @cmd = (undef, $decompress ? qw(-dc) : qw(-c));
        require PublicInbox::Spawn;
        for my $exe (@info) {
@@ -172,9 +172,23 @@ sub zsfx2cmd ($$$) {
                $cmd[0] = PublicInbox::Spawn::which($exe) and last;
        }
        $cmd[0] // die join(' or ', @info)." missing for .$zsfx";
-       # push @cmd, @{$cmd_opt->{-default}} if $cmd_opt->{-default};
-       for my $bool (qw(rsyncable)) {
-               my $switch = $cmd_opt->{rsyncable} // next;
+
+       # not all gzip support --rsyncable, FreeBSD gzip doesn't even exit
+       # with an error code
+       if (!$decompress && $cmd[0] =~ m!/gzip\z! && !defined($cmd_opt)) {
+               pipe(my ($r, $w)) or die "pipe: $!";
+               open my $null, '+>', '/dev/null' or die "open: $!";
+               my $rdr = { 0 => $null, 1 => $null, 2 => $w };
+               my $tst = [ $cmd[0], '--rsyncable' ];
+               my $pid = PublicInbox::Spawn::spawn($tst, undef, $rdr);
+               close $w;
+               my $err = do { local $/; <$r> };
+               waitpid($pid, 0) == $pid or die "BUG: waitpid: $!";
+               $cmd_opt = $err ? {} : { rsyncable => '' };
+               push(@$x, $cmd_opt);
+       }
+       for my $bool (keys %$cmd_opt) {
+               my $switch = $cmd_opt->{$bool} // next;
                push @cmd, '--'.($switch || $bool);
        }
        for my $key (qw(rsyncable)) { # support compression level?