Ability during pull requests to see the original code reviewed

USER STORY: The moderator sometimes needs to see exactly what the original reviewers saw. This basically just ignores any new changes since the bookmark change set. Again, this can kind-of be done in Stash today. I do so by selecting the tagged change set and then diff with develop. However, new changes on develop (from other feature branches) end up being displayed.

• FEATURE REQUEST: Ability to view the exact state of code at the bookmark. Seems like this should diff the tagged change set to the develop branch, but carefully select the change set on the develop branch to avoid showing changes after the latest merge.