E.g. on a fresh ubuntu machine, I\'ve just run sudo apt-get git, and there\'s no completion when typing e.g. git check[tab].
I didn\'t find
On Github in the Git project, They provide a bash file to autocomplete git commands.
You should download it to home directory and you should force bash to run it. It is simply two steps and perfectly explained(step by step) in the following blog post.
code-worrier blog: autocomplete-git/
I have tested it on mac, it should work on other systems too. You can apply same approach to other operating systems.