Some pull requests can be quite complicated and span many files. In these cases I find it useful to review file by file in Diff mode before approving the pull request. The problem with this is when reviewing over time, or in a very distracting environment, its easy to forget which files I have already reviewed. Using comments I can sort of accomplish this but it would be nice to have an approve file option in Diff mode for my own tracking. This would have no impact on the pull request itself. After approving every file, Bitbucket could possibly show a modal asking if I want to approve the pull request, however other than that no changes to pull request approvals would be needed.