I'm a bit concerned about this line because I had to add it just to make the specs pass. Does not feel right to me.
Without it `File.expand_path` will prefix `file` with the current working directory on my Linux which then leads to the spec failing because it cannot match `C:/Users/foo/project/log/foo.rb`.

My solution would be to move it within the first `unless` statement:
```ruby
unless file.start_with?('/') || file.match('^[A-Z]:/')
  file = File.join(Dir.pwd, file)
  file = File.expand_path(file)
end
```
But that would require `file` to always be a absolute path. I think this cannot be guaranteed and it would make the use of `File.expand` pointless.

What do you think?