$ brew install bash-completion
$ brew tap homebrew/completions
if [ -f $(brew --prefix)/etc/bash_completion ]; then
. $(brew --prefix)/etc/bash_completion
fi
cd /usr/local/etc/bash_completion.d
ln -s /Applications/Docker.app/Contents/Resources/etc/docker.bash-completion
ln -s /Applications/Docker.app/Contents/Resources/etc/docker-machine.bash-completion
ln -s /Applications/Docker.app/Contents/Resources/etc/docker-compose.bash-completion