网上找了很多文章都不行，最后自己摸索找到了可以有用的命令，talk is cheap， 上代码：

brew install homebrew/cask/meld

执行以后就可以看到在安装对应的包了：

brew install homebrew/cask/meld
==> brew cask install homebrew/cask/meld 
==> Downloading https://github.com/yousseb/meld/releases/download/osx-19/meldmerge.dmg
==> Downloading from https://github-production-release-asset-2e65be.s3.amazonaws.com/28624006/66cb2580-7e5                                                                                                             

更新: 现在墙越来越高，github很难访问，得搭梯子才能下载下来了