The entire lifetime of that version will stay on that branch.
Development is generally done on branch 'master'. Major Moodle versions each have their own branch in Git. Once you have downloaded and installed your OS relevant git installation, the git commands in this document should work with your operating system. Support for Git was, up until recently, mostly confined to Linux but builds are now available for most popular operating systems: Getting hold of Git (Windows, OSX, Linux and others)
