merge_path

# File lib/uri/generic.rb, line 990
    def merge_path(base, rel)

      # RFC2396, Section 5.2, 5)
      # RFC2396, Section 5.2, 6)
      base_path = split_path(base)
      rel_path  = split_path(rel)

      # RFC2396, Section 5.2, 6), a)
      base_path << '' if base_path.last == '..'
      while i = base_path.index('..')
        base_path.slice!(i - 1, 2)
      end

      if (first = rel_path.first) and first.empty?
        base_path.clear
        rel_path.shift
      end

      # RFC2396, Section 5.2, 6), c)
      # RFC2396, Section 5.2, 6), d)
      rel_path.push('') if rel_path.last == '.' || rel_path.last == '..'
      rel_path.delete('.')

      # RFC2396, Section 5.2, 6), e)
      tmp = []
      rel_path.each do |x|
        if x == '..' &&
            !(tmp.empty? || tmp.last == '..')
          tmp.pop
        else
          tmp << x
        end
      end

      add_trailer_slash = !tmp.empty?
      if base_path.empty?
        base_path = [''] # keep '/' for root directory
      elsif add_trailer_slash
        base_path.pop
      end
      while x = tmp.shift
        if x == '..'
          # RFC2396, Section 4
          # a .. or . in an absolute path has no special meaning
          base_path.pop if base_path.size > 1
        else
          # if x == '..'
          #   valid absolute (but abnormal) path "/../..."
          # else
          #   valid absolute path
          # end
          base_path << x
          tmp.each {|t| base_path << t}
          add_trailer_slash = false
          break
        end
      end
      base_path.push('') if add_trailer_slash

      return base_path.join('/')
    end