(https://github.com/ruby/irb/pull/824)

* Command is not a method

* Fix command test

* Implement non-method command name completion

* Add test for ExtendCommandBundle.def_extend_command

* Add helper method install test

* Remove spaces in command input parse

* Remove command arg unquote in help command

* Simplify Statement and handle execution in IRB::Irb

* Tweak require, const name

* Always install CommandBundle module to main object

* Remove considering local variable in command or expression check

* Remove unused method, tweak

* Remove outdated comment for help command arg

Co-authored-by: Stan Lo <stan001212@gmail.com>

---------

https://github.com/ruby/irb/commit/8fb776e379

Co-authored-by: Stan Lo <stan001212@gmail.com>

(https://github.com/ruby/irb/pull/873)

* Replace ExtendCommand with Command and standardize command related names

1. Rename lib/irb/extend-command.rb to lib/irb/command.rb
2. Rename lib/irb/cmd/*.rb to lib/irb/command/*.rb
3. Rename test/irb/test_cmd.rb to test/irb/test_command.rb
4. Rename ExtendCommand to Command

* Alias ExtendCommand to Command and deprecate it

* Rename Command::Nop to Command::Base

* Not deprecate old constants just yet

* Add lib/irb/cmd/nop.rb back

https://github.com/ruby/irb/commit/462c1284af