my $cmd = [ 'git', "--git-dir=$git->{git_dir}",
qw(merge-base --is-ancestor), $cur, $tip ];
my $pid = spawn($cmd);
- defined $pid or die "spawning ".join(' ', @$cmd)." failed: $!";
waitpid($pid, 0) == $pid or die join(' ', @$cmd) .' did not finish';
$? == 0;
}