Magit-tbdiff is a Magit interface to git-tbdiff and git-range-diff, subcommands for comparing two versions of a topic branch (or more generally two ranges). When Magit-tbdiff was created, only git-tbdiff, a third-party extension, existed. However, recent versions of Git include a tbdiff-inspired range-diff subcommand. Using range-diff is recommended, and it will be used by default if detected.

The commentary in magit-tbdiff.el provides an overview of Magit-tbdiff commands.