merge_path

# File lib/uri/generic.rb, line 618
    def merge_path(base, rel)
      # RFC2396, Section 5.2, 5)
      if rel[0] == ?/ #/
        # RFC2396, Section 5.2, 5)
        return rel

      else
        # 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 base_path.empty?
          base_path = [''] # keep '/' for root directory
        else
          base_path.pop
        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 = true
        while x = tmp.shift
          if x == '..' && base_path.size > 1
            # RFC2396, Section 4
            # a .. or . in an absolute path has no special meaning
            base_path.pop
          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
    end