os.exit(nil)

[Egor Skriptunoff <egor.skriptunoff@...>]

Returning nil or meaningful value is common in Lua.
But os.exit(nil) is unexpectedly equivalent to os.exit(true), not
os.exit(false).
This forces us to write
os.exit(foo() or false)
instead of more concise and clear
os.exit(foo()).
My suggestion is to make os.exit(nil) different from os.exit().