Refactor Preview doesn't render newly created file content

[marrej]

TLDR: Refactor preview should render out the content for createFile/deleteFile not only for replace/insert/delete

Refactor preview currently doesn't render createFile content, instead it only renders an empty widget.

This makes it hard for users to understand what is being accepted in this case, and I would argue that the contents should be shown. Same goes for the deleteFiles. If users don't see the original file content that is being deleted they need an extra click to jump in to the file to observe what actually is being deleted.