def location_in_cache( revision = nil )
      begin
        elements = [cache, repo_type, split_url, revision].flatten.compact.collect { |i| i.to_s } 
        File.join( elements )
      rescue => e
        raise CacheCalculationError.new(e.msg + e.backtrace.to_s)
      end
    end
def location_in_cache( revision = nil )
      begin
        elements = [cache, repo_type, split_url, revision].flatten.compact.collect { |i| i.to_s } 
        File.join( elements )
      rescue => e
        raise CacheCalculationError.new(e.msg + e.backtrace.to_s)
      end
    end
Calculates the location of a cached checkout