https://github.com/ruby/irb/commit/2057248e40

(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

(https://github.com/ruby/irb/pull/872)

See #787 for more details.

https://github.com/ruby/irb/commit/d9192d92d0

(https://github.com/ruby/irb/pull/869)

Currently, if the signature's constant part is not defined, a NameError
would be raised.

```
irb(main):001> show_source Foo
(eval):1:in `<top (required)>': uninitialized constant Foo (NameError)

Foo
^^^
        from (irb):1:in `<main>'
```

This commit fixes the issue and simplifies the `edit` command's implementation.

https://github.com/ruby/irb/commit/8c16e029d1

(https://github.com/ruby/irb/pull/862)

* Powerup show_source by enabling RubyVM.keep_script_lines

* Add file_content field to avoid reading file twice while show_source

* Change path passed to eval, don't change irb_path.

* Encapsulate source coloring logic and binary file check insode class Source

* Add edit command testcase when irb_path does not exist

* Memoize irb_path existence to reduce file existence check calculating eval_path

https://github.com/ruby/irb/commit/239683a937

(https://github.com/ruby/irb/pull/868)

* Fix exit! command warning and method behavior

* Remove arg(0) from Kernel.exit and Kernel.exit!

https://github.com/ruby/irb/commit/372bc59bf5

(https://github.com/ruby/irb/pull/867)

* Remove IRB.irb_exit! method

It's not necessary to introduce a new method just for the exit! command
at this moment.

* Rename ExitForcedAction to ForceExit

* Move force exit tests to a dedicated file

* Fix nested history saving with exit! command

Because we switched to use `Kernel#exit` instead of `exit!`, the outer
session's ensure block in `Irb#run` will be run, which will save the
history. This means the separate check to save history when force exiting
is no longer necessary.

* execute_lines helper should also capture IRB setup's output

This prevents setup warnings from being printed to test output
while allowing those output to be tested.

* Update readme

https://github.com/ruby/irb/commit/899d10ade1

(https://github.com/ruby/irb/pull/851)

* Added failing test for when writing history on exit

* Save history on exit

* Exit early when calling Kernel.exit

* use status 0 for kernel.exit

* Added test for nested sessions

* Update lib/irb.rb

---------

https://github.com/ruby/irb/commit/c0a5f31679

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

(https://github.com/ruby/irb/pull/835)

* Remove unnecessary code from the exit command's implementation

1. The parameters of `IRB.irb_exit` were never used. But there are some
   libraries seem to call it with arguments + it's declared on the top-level
   IRB constant. So I changed the params to anonymous splat instead of removing them.
2. `Context#exit` was completely unnecessary as `IRB.irb_exit` doesn't use
   the `@irb` instance it passes. And since it's (or should be treated as)
   a private method, I simply removed it.
3. The `exit` command doesn't use the status argument it receives at all.
   But to avoid raising errors on usages like `exit 1`, I changed the argument to
   anonymous splat instead removing it.

* Make exit an actual command

* Update readme

https://github.com/ruby/irb/commit/452b543a65

(https://github.com/ruby/irb/pull/813)

https://github.com/ruby/irb/commit/e79a90a1e6