code: @Nonnull
    public DescribeCommand abbrev(@Nullable Integer n) {
      if (n != null) {
        Preconditions.checkArgument(n < 41, String.format("N (commit abbrev length) must be < 41. (Was:[%s])", n));
        Preconditions.checkArgument(n >= 0, String.format("N (commit abbrev length) must be positive! (Was [%s])", n));
        log.info("--abbrev = {}", n);
        abbrev = n;
      }
      return this;
    }
docs: <pre>--abbrev=N</pre>
  
  Instead of using the default <em>7 hexadecimal digits</em> as the abbreviated object name,
  use <b>N</b> digits, or as many digits as needed to form a unique object name.
  
  An `n` of 0 will suppress long format, only showing the closest tag.