It focuses on reviewing the evolution of individual commits within a branch, rather than a unified diff of the entire branch, allowing you to split up even large reviews into smaller, easier to review, better documented patches. Butler Review is a commit based, chat centered review system where each commit in a branch is treated as an independently reviewable patch and the branch is seen as an evolving series of patches rather than a unified diff. The biggest change in focus with Butler Review versus the branch-based review of Pull/Merge Requests is that each commit is treated as an individually reviewable patch to the codebase.