fatal: not in a git directory
Error: Command failed with exit 128: git
首先 网上说的那个git config 是没用的，我是在brew -v 正常的情况下，出现这个错误的，
所以，继续搜索...
解决：
执行 brew doctor，然后按照提示，把所有的warnning消除掉，然后就正常了
brew doctor
Your system is ready to brew.
brew update --verbose
Checking if we need to fetch /opt/homebrew/Homebrew...
Fetching /opt/homebrew/Homebrew...
Checking if we need to fetch formula.jws.json...
Checking if we need to fetch cask.jws.json...
Checking if we need to fetch formula_tap_migrations.jws.json...
Checking if we need to fetch cask_tap_migrations.jws.json...
Already up-to-date.