GIT is a "directory content manager" designed to handle absolutely massive projects with speed and efficiency, and the release of the 2.6.12 (and later) versions of the Linux kernel as well as more and more other projects switching to it would indicate that it does this task well. GIT falls in the category of distributed source code management tools, similar to e.g. GNU Arch or Monotone (or, in the commercial world, BitKeeper). Every GIT working directory is a full-fledged repository with full revision tracking capabilities, not dependent on network access to a central server.
WWW: https://git-scm.com/