Ruby Pathname extensions to check for parent and subdirectory: Pathname.under? and Pathanme.above?

gistfile1.rb

class Pathname
  def under?(path)
    parent, child = [ Pathname.new(path), self ].inject([]) { |a, p| a << p.expand_path.to_s.split(File::SEPARATOR) }
    parent.drop_while { |p| p == child.shift }.none? && child.any?
  end

  def above?(path)
    Pathname.new(path).under? self
  end
end

Pathname.new("/usr/local/bin/emacs").under? "/usr"  # true
Pathname.new("/Users/sshaw").above? "./sshaw/perl"  # true