Accepting pull request on a file-per-file basis

Whenever I review a larger pull request (50+ files), I feel the need to accept each file individually. This would help to split a pull request over time and then still knowing what of it was already done. I also often scroll down to other files, which need to be reviewed logically before the previous ones. When going over the full pull request, it would very much help to see those files as already accepted.

This could be done with a comment, but comments in our environment are used to address an issue and to notify the creator of the pull requests. It would make it impossible to notify the other person if each file had an additional comment just to mark it as done.

So, I would really enjoy, if you'd add a checkbox to each file in a pull request.