The interesting moment is that `cd -` is still a bit dorky.
[1] pry(main)> _pry_.repl :a
[2] pry(:a):1> _pry_.repl :b
[3] pry(:b):2> cd -
[4] pry(:b):2> cd -
[5] pry(:b):2>
The problem is that `_pry_.repl` pushes a new binding onto
`binding_stack`, however, it knows nothing about `old_stack`.
Well, there is a workaround for this.
[1] pry(main)> _pry_.repl :a
[2] pry(:a):1> ^D
[3] pry(main)> cd -
[4] pry(:a):1> cd -
[5] pry(main)>
Fix "undefined method `old_stack=' for nil:NilClass" error in this
commit, when you press ^D in a nested REPL. Add a test case for this.
Rewrite some comments and old Control-D units tests (so they use newer
test API).
Signed-off-by: Kyrylo Silin <kyrylosilin@gmail.com>
