What version are you running?
Review Board 2.0.15
What's the URL of the page this enhancement relates to, if any?

Describe the enhancement and the motivation for it.
I would like to have ability to expand/collapse whole file content in view diff mode.

When I have svn commit with a lot of files, it will dramatically increase my ability of moving between files.

Now i can click on file link at the top to move between files. In the same time I would like to collapse some files that i am not interested at this moment. 
What operating system are you using? What browser?
not importatn
Please provide any additional information below.