I need to do a code review of a whole branch in GitHub. I went to the branches page and hit compare. There’s a tab there, files changed, that shows exactly what I need, the diff between the two branches, master and the selected one. The problem is that it doesn’t allow you to comment on code like a single diff does:

The blue bubble just doesn’t appear on the branch diff page.
Does anybody know how to perform a code review of a whole branch in GitHub?
Thanks.
Apparently there’s no UI to write comments on a branch diff. My solution for now was asking the other programmer to do a pull request. It did work to do a pull request from one project to itself and in the pull request I can write comments.