Fix config files in ancestor dirs are ignored if another exists in home

[yujinakayama]

This fixes a bug below:

• You have ~/.rubocop.yml in your home directory
• There is project/.rubocop.yml
• There is project/example.rb
• Execute rubocop in project directory

In this situation, ~/.rubocop.yml is always used and project/.rubocop.yml is never used.

[bbatsov]

The code looks good to me. @jonas054, would you like to share your thoughts as well?

[jonas054]

Yes, I'm responsible for that bug. I think I made config_from_dotfile too complicated by doing caching and search logic in one method. I might want to think about refactoring it later. Anyway, it's a good correction. Thanks @yujinakayama!

[bbatsov]

Thanks!