Move built-ins to a separate class

ruby/builtins.rb

@@ -1,5 +1,12 @@
 class Shell
-  def exec_builtin(name, args)
+  class Builtins
+    attr_reader :logger
+
+    def initialize(logger)
+      @logger = logger
+    end
+
+    def exec(name, args)
       send(:"builtin_#{name}", args)
     end
 
@@ -28,4 +35,5 @@ class Shell
     def bulitin_pwd(_args)
       puts Dir.pwd
     end
+  end
 end

ruby/main.rb

@@ -15,6 +15,7 @@ class Shell
     @logger = ShellLogger.new
     @options = parse_options(args)
     @jobs_by_pid = {}
+    @builtins = Builtins.new(@logger)
     logger.verbose "options: #{options.inspect}"
   end
 
@@ -95,9 +96,9 @@ class Shell
       exit 0
     when ''
       # noop
-    when builtin?(argv0)
+    when @builtins.builtin?(argv0)
       args.shift
-      exec_builtin(argv0, args)
+      @builtins.exec(argv0, args)
     else
       status = exec_command(cmd)
       print "#{RED}-#{status}-#{CLEAR} " unless status.zero?

ruby/shell_logger.rb

@@ -5,10 +5,6 @@ class ShellLogger
 
   attr_reader :logs
 
-  def self.instance
-    @instance ||= new
-  end
-
   def initialize
     clear
   end