preserve local variables across 'cd' in pry

.pryrc

class Pry::Command::Cd
  def _binding
    _pry_.binding_stack.last
  end

  def save_local_variables(key, b)
    state.locals ||= {}
    builtin_locals = [:__, :_, :_dir_, :_file_, :_ex_, :_pry_, :_out_, :_in_]
    _local_variables = b.eval('local_variables')

    state.locals[key] = (_local_variables - builtin_locals).map do |var|
      [var, b.local_variable_get("#{var}")]
    end.to_h
  end

  def restore_local_variables(key, b)
    state.locals[key] && state.locals[key].each do |var, val|
      _pry_.inject_local("#{var}", val, b)
    end
  end
end

Pry.hooks.add_hook(:before_cd, 'before_cd_hook') do
  save_local_variables _binding.eval('self'), _binding
end

Pry.hooks.add_hook(:after_cd, 'after_cd_hook') do
  restore_local_variables _binding.eval('self'), _binding
end