Add disable_irb command to disable debug of binding.irb (#898)

* Add disable_irb command to disable debug of binding.irb

* disable_irb doesn't override Kernel.exit

Kernel.exit call is removed because disable_irb does not override Kernel.exit
and workaround to https://bugs.ruby-lang.org/issues/18234 is not needed.

Author: hogelog

lib/irb/command.rb

@@ -196,7 +196,12 @@ def irb_context
         :irb_history, :History, "command/history",
         [:history, NO_OVERRIDE],
         [:hist, NO_OVERRIDE],
-      ]
+      ],
+
+      [
+        :irb_disable_irb, :DisableIrb, "command/disable_irb",
+        [:disable_irb, NO_OVERRIDE],
+      ],
     ]
 
 

lib/irb/command/disable_irb.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module IRB
+  # :stopdoc:
+
+  module Command
+    class DisableIrb < Base
+      category "IRB"
+      description "Disable binding.irb."
+
+      def execute(*)
+        ::Binding.define_method(:irb) {}
+        IRB.irb_exit
+      end
+    end
+  end
+
+  # :startdoc:
+end