参考地址：
https://gist.github.com/johngibb/972430
将如下内容保存成 install-git-completion.sh 文件，加入执行权限后执行
URL="https://raw.githubusercontent.com/git/git/master/contrib/completion/git-completion.bash"
PROFILE="$HOME/.profile"
echo "Downloading git-completion..."
if ! curl "$URL" --silent --output "$HOME/.git-completion.bash"; then
echo "ERROR: Couldn't download completion script. Make sure you have a working internet connection." && exit 1
fi
SOURCE_LINE="source ~/.git-completion.bash"
if [[ -f "$PROFILE" ]] && grep -q "$SOURCE_LINE" "$PROFILE"; then
echo "Already added to bash profile."
else
echo "Adding to bash profile..."
echo "$SOURCE_LINE" >> "$PROFILE"
fi
echo "Reloading bash profile..."
source "$PROFILE"
echo
echo "Successfully installed."
echo "Git auto-completion should be all set!"
