Mac brew更换源

之所以更换国内源，是因为brew安装软件时，常常因为网络问题导致安装失败！

1. [清华大学镜像]，资源丰富，速度快。

2. [替换现有上游]

   git -C "$(brew --repo)" remote set-url origin https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/brew.git
   
   git -C "$(brew --repo homebrew/core)" remote set-url origin https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/homebrew-core.git
   
   git -C "$(brew --repo homebrew/cask)" remote set-url origin https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/homebrew-cask.git
   
   brew update
   

3. [复原]

   git -C "$(brew --repo)" remote set-url origin https://github.com/Homebrew/brew.git
   
   git -C "$(brew --repo homebrew/core)" remote set-url origin https://github.com/Homebrew/homebrew-core.git
   
   git -C "$(brew --repo homebrew/cask)" remote set-url origin https://github.com/Homebrew/homebrew-cask.git
   
   brew update