plus

# File lib/pathname.rb, line 619
  def plus(path1, path2) # -> path
    prefix2 = path2
    index_list2 = []
    basename_list2 = []
    while r2 = chop_basename(prefix2)
      prefix2, basename2 = r2
      index_list2.unshift prefix2.length
      basename_list2.unshift basename2
    end
    return path2 if prefix2 != ''
    prefix1 = path1
    while true
      while !basename_list2.empty? && basename_list2.first == '.'
        index_list2.shift
        basename_list2.shift
      end
      break unless r1 = chop_basename(prefix1)
      prefix1, basename1 = r1
      next if basename1 == '.'
      if basename1 == '..' || basename_list2.empty? || basename_list2.first != '..'
        prefix1 = prefix1 + basename1
        break
      end
      index_list2.shift
      basename_list2.shift
    end
    r1 = chop_basename(prefix1)
    if !r1 && /#{SEPARATOR_PAT}/ =~ File.basename(prefix1)
      while !basename_list2.empty? && basename_list2.first == '..'
        index_list2.shift
        basename_list2.shift
      end
    end
    if !basename_list2.empty?
      suffix2 = path2[index_list2.first..-1]
      r1 ? File.join(prefix1, suffix2) : prefix1 + suffix2
    else
      r1 ? prefix1 : File.dirname(prefix1)
    end
  end