#!/usr/bin/perl
# given a perforce change number, output the equivalent git commit id
# with -c, checks out the specified commit
die "usage: $0 [-c|--checkout] [git-log-options] changenum" unless @ARGV;
my $num = 1;
my $checkout = 0;
my $before = '--before=2008-12-18'; # only changes made under perforce
for (@ARGV) {
        m{^\d+$} && (($change,$_) = ($_,undef));
        m{^-\d+$} && (($num,$_) = (-$_,undef));
        $_ eq '-c' || $_ eq '--checkout'
            and $checkout = 1;
}
my $grep = "--grep=^p4raw-id:.*\@$change\$";
@ARGV = grep { defined } @ARGV;
if ($checkout) {
    my $commit = qx(git rev-list -1 --all $before '$grep');
    chomp $commit;
    die "no commit found" unless $commit;
    system(git => checkout => $commit);
}
else {
    if ( -t STDOUT or @ARGV ) {
        system(qw(git log), $grep, "-$num", "--all", $before, @ARGV);
    }
    else {
        system(qw(git rev-list -1 --all), $before, $grep);
    }
}