Create a .git_settings directory in (actually you can choose any):
Users/username/
copy following file from git sources:
git_source_files/contrib/completion/git-completion.bash
execute following command to edit bashrc file:
mate /etc/bashrc
and add following lines:
#git autocompletion source ~/.git_settings/git-completion.bash
Now you can go to your repository and type:
git st<tab>