brew install bash-completion
echo '[[ -r "/usr/local/etc/profile.d/bash_completion.sh" ]]
&& . "/usr/local/etc/profile.d/bash_completion.sh"' >> .bash_profile
Use it
git checkout *word*
echo 'autoload -Uz compinit && compinit
autoload -Uz vcs_info' >> .zshrc
It will suggest all git commands, branch names.