There are a few folks who would like to use Git for the project, including me, but it's not the top of our priority list.
You can get some of the benefits of Git by looking at or even cloning our GitHub mirror.
One of my favorite uses: tracking changes to an individual package.
Steps1 - Navigate to a package of interest, say unittest.
This is a great way to see what changes have happened since the latest release of a package or just to track individual parts of the Dart project.