```ruby
require "shellwords"

module Rubycritic
  module SourceControlSystem

    class Base
      @@systems = []

      def self.register_system
        @@systems << self
      end

      def self.systems
        @@systems
      end

      def self.create
        supported_system = systems.detect(&:supported?)
        if supported_system
          supported_system.new
        else
          puts "Rubycritic requires a #{system_names} repository."
          Double.new
        end
      end

      def self.system_names
        systems.join(", ")
      end

      def self.supported?
        raise NotImplementedError.new("The #{self.class} class must implement the #{__method__} method.")
      end

      def revisions_count(path)
        raise NotImplementedError.new("The #{self.class} class must implement the #{__method__} method.")
      end

      def date_of_last_commit(path)
        raise NotImplementedError.new("The #{self.class} class must implement the #{__method__} method.")
      end

      def has_revision?
        raise NotImplementedError.new("The #{self.class} class must implement the #{__method__} method.")
      end

      def head_reference
        raise NotImplementedError.new("The #{self.class} class must implement the #{__method__} method.")
      end

      def travel_to_head
        raise NotImplementedError.new("The #{self.class} class must implement the #{__method__} method.")
      end
    end

  end
end

require "rubycritic/source_control_systems/double"
require "rubycritic/source_control_systems/git"
require "rubycritic/source_control_systems/mercurial"
```

Improve message displayed when no SCS is found
user
```ruby
require "shellwords"

module Rubycritic
  module SourceControlSystem

    class Base
      @@systems = []

      def self.register_system
        @@systems << self
      end

      def self.systems
        @@systems
      end

      def self.create
        supported_system = systems.detect(&:supported?)
        if supported_system
          supported_system.new
        else
          puts "RubyCritic can provide more feedback if you use a #{connected_system_names} repository."
          Double.new
        end
      end

      def self.connected_system_names
        "#{systems[0...-1].join(', ')} or #{systems[-1]}"
      end

      def self.supported?
        raise NotImplementedError.new("The #{self.class} class must implement the #{__method__} method.")
      end

      def revisions_count(path)
        raise NotImplementedError.new("The #{self.class} class must implement the #{__method__} method.")
      end

      def date_of_last_commit(path)
        raise NotImplementedError.new("The #{self.class} class must implement the #{__method__} method.")
      end

      def has_revision?
        raise NotImplementedError.new("The #{self.class} class must implement the #{__method__} method.")
      end

      def head_reference
        raise NotImplementedError.new("The #{self.class} class must implement the #{__method__} method.")
      end

      def travel_to_head
        raise NotImplementedError.new("The #{self.class} class must implement the #{__method__} method.")
      end
    end

  end
end

require "rubycritic/source_control_systems/double"
require "rubycritic/source_control_systems/git"
require "rubycritic/source_control_systems/mercurial"
```
assistant