void pathdecode(stralloc *fn)
{
  int i;
  int j;
  char ch;

  j = 0;
  for (i = 0;i < fn->len;++i) {
    ch = fn->s[i];
    if (ch == 0) ch = '\n';
    if (j && (fn->s[j - 1] == '/')) {
      if (ch == '.') ch = ':';
      if (ch == '/') continue;
    }
    fn->s[j++] = ch;
  }
  fn->len = j;
}