code: @Nonnull
    public DescribeCommand dirty(@Nullable String dirtyMarker) {
      Optional<String> option = Optional.ofNullable(dirtyMarker);
      log.info("--dirty = {}", option.orElse(""));
      this.dirtyOption = option;
      return this;
    }
docs: <pre>--dirty[=mark]</pre>
  Describe the working tree. It means describe HEAD and appends mark (<pre>-dirty</pre> by default) if the
  working tree is dirty.
  
  @param dirtyMarker the marker name to be appended to the describe output when the workspace is dirty
  @return itself, to allow fluent configuration