(https://github.com/ruby/irb/pull/888)
* Remove dead irb_level method
* Restructure workspace management
Currently, workspace is an attribute of IRB::Context in most use cases.
But when some workspace commands are used, like `pushws` or `popws`, a
workspace will be created and used along side with the original workspace
attribute.
This complexity is not necessary and will prevent us from expanding
multi-workspace support in the future.
So this commit introduces a @workspace_stack ivar to IRB::Context so IRB
can have a more natural way to manage workspaces.
* Fix pushws without args
* Always display workspace stack after related commands are used
61560b99b3
(https://github.com/ruby/irb/pull/623)
* Rename `ext/history.rb` to `ext/eval_history.rb`
To confusion with `lib/irb/history.rb`
* Add eval_history tests
* Rename eval_history's History to EvalHistory to avoid confusion
