sub sort_files {
        my $adir = $1 if $$a{path} =~ m/^(.*)\//;
        my $bdir = $1 if $$b{path} =~ m/^(.*)\//;

        # a and b in the same dir
        if ($adir eq $bdir) {
                if ($$a{'file'} && !$$b{'file'}) {
                        return -1;
                } elsif (!$$a{'file'} && $$b{'file'}) {
                        return 1;
                }
                return lc $$a{'path'} cmp lc $$b{'path'};
        }

        # b in subdir of a
        if ($bdir =~/^$adir\// && $$a{'file'} && !$$b{'file'}) {
                return -1;
        # a in subdir of b
        } elsif ($adir =~/^$bdir\// && $$b{'file'} && !$$a{'file'}) {
                return 1;
        }

        lc $$a{'path'} cmp lc $$b{'path'};
}