Reviews in forked repos that track upstream changes
Some workflows require overwriting a PR's target branch with the head branch when it's ready to merge — for example if you're maintaining a fork and rebasing from the upstream master. Currently, both GitHub and Reviewable will pick the wrong base commit to compare files with in this scenario, showing not only the upstream changes but also all the extra changes made in your fork over time.
You can now get the diff you likely want by adding a Merge manually by overwriting target label to your pull request. This will cause Reviewable to compare files against the target branch's current head, showing upstream changes and any conflicts you resolved while rebasing, while leaving out modifications in your fork that survived unscathed. (For best results, add the label to the PR when you first create it.)