Ability to review diff between two versions of PR is a great missing feature in GitHub. When dealing with large changes, GitLab review flow is IMHO easier for reviewer. Gitlab store each push of a MR branch as different version (as hidden refs), which make the feature possible. In GH, you force push a branch, you loose the old code for good, so reviewer has to remember why he did that comment before to see if it is still relevant.
This is such an important feature that has a direct impact on code quality and time savings that I'm not sure why it isn't a priority feature. As a reviewer, having to choose between "review everything again" or "trust the submitter didn't introduce extra changes in the revised pr" is such a terrible choice to have to make.
In the top left, there should be a "changes from..." drop down menu that will let you choose which commits you want to view. The default is "changes from all commits".
If you're on GitHub Enterprise, availability will depend on the last time your company has installed updates.
That is not the same feature.
It requires you to always add your fix in a new commit add opposed to amending the commits and maintain a clear purposed commit list.
I think the more official Git way of doing it would be to collect all the changes in separate commits, and then squash merge them at the end of the code review.
