route_namespace_pattern

# File railties/lib/rails/generators/actions.rb, line 517
        def route_namespace_pattern(namespace)
          namespace.each_with_index.reverse_each.reduce(nil) do |pattern, (name, i)|
            cummulative_margin = "\\#{i + 1}[ ]{2}"
            blank_or_indented_line = "^[ ]*\n|^#{cummulative_margin}.*\n"
            "(?:(?:#{blank_or_indented_line})*?^(#{cummulative_margin})namespace :#{name} do\n#{pattern})?"
          end.then do |pattern|
            /^([ ]*).+\.routes\.draw do[ ]*\n#{pattern}/
          end
        end