IRB doesn't save input history when exited with exit!

[st0012]

Because IRB relies on IRB.conf[:AT_EXIT] config, which will be run in at_exit, to save a session's input history. When users exit the session with exit!, the input is not written.

Reproduction Steps

1. Open an IRB session and run

   irb(main):001:0> a = 1
   => 1
   irb(main):002:0> b = 2
   => 2
   irb(main):003:0> exit
   

2. Open another session and type up-arrow to check the above history

3. In the same session, run

   irb(main):001:0> c = 3
   => 3
   irb(main):002:0> d = 4
   => 4
   irb(main):003:0> exit! # with a ! this time
   

4. Open another session and type up-arrow to view history

Expected Behaviour

Input from step 3 should be part of the history

Actual Behaviour

Input from step 3 is lost

[tompng]

This is the expected behavior of Kernel.exit!. Skips all at_exit handlers and ensure statements.
I think we can add exit! command that executes Kernel.exit

[st0012]

I'm thinking about the other direction: we patch Kernel.exit! to save history instead.
In some cases, users may want to skip at_exit hooks when they exit the session, like when debugging at_exit issues that hang the program. If we make exit! the same as exit, then there's no obvious way to leave the session without the hang (ofc, they can call Kernel.exit! manually but it's not intuitive).

[tompng]

Just for my case, most of the time I use exit! is when I want to just Kernel.exit because exit is overridden in irb.
like

loop{
  ...
  binding.irb # want to exit the program after debugging/investigating. don't want to skip cleanup (ensure, at_exit)
}