def bump
    segments = self.segments.dup
    segments.pop while segments.any? { |s| String === s }
    segments.pop if segments.size > 1

    segments[-1] = segments[-1].succ
    self.class.new segments.join(".")
  end
#
Return a new version object where the next to the last revision
number is one greater (e.g., 5.3.1 => 5.4).

Pre-release (alpha) parts, e.g, 5.3.1.b.2 => 5.4, are ignored.