It's Magit! A Git Porcelain inside Emacs.
Another one already!
Finally, a release!
Note to distributors: The v in the name of the tarball and its top-level directory was added by mistake. The next release won't have it.
(Github orders this wrong. This release came before v2.90.0 (by every messure: graph, commit date, tag date, and creating this thing here date).