步骤一
cd “$(brew --repo)”
git remote set-url origin https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/brew.git
步骤二
cd “$(brew --repo)/Library/Taps/homebrew/homebrew-core”
git remote set-url origin https://mirrors.tuna.tsinghua.edu.cn/git/homebrew/homebrew-core.git
#步骤三
brew update
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注意这里需要等待一会，因为要更新资源。
更新完后使用brew update，brew install速度变快很多了，不会卡在那半天没动静，替换镜像完成。
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还原brew
cd “$(brew --repo)”
git remote set-url origin https://github.com/Homebrew/brew.git
cd “$(brew --repo)/Library/Taps/homebrew/homebrew-core”
git remote set-url origin https://github.com/Homebrew/homebrew-core
brew update
