My personal best tool for a Git branch's code review is `git lfo`, where the alias expands to:

    git log --pretty=full --reverse --show-notes=* -p --abbrev-commit origin/master..

Coupled with a "good diff highlighter", i.e. `diff-highlight | less --tabs=4 -RFX`… I'm set.

I've yet to see a tool that allows me to review all commits as well as code, as easily.

I don't only review a branch as a whole, i.e. `git diff master`, or "here's the diff" from a pull request… but I also review each commit individually (and rebase/amend them when required), as commits need to be in tip-top shape to end up going into master.