The new Working Copy beta lists pull requests from GitHub, GitLab and Bitbucket, lets you comment on lines, submit a review, merge and close.

The diff analysis is deterministic and runs on your device: changes that only touch whitespace or rename something are folded away, so you read only what really changed.

Looking for testers who review code from colleagues or agents:
https://testflight.apple.com/join/VduxyR5a