homebrew-core is a shallow clone.

https://www.jianshu.com/p/f2a4994b3866

解决的方法

cd /usr/local/Homebrew/Library/Taps/homebrew
rm -rf homebrew-core
rm -rf homebrew-cask
brew upgrade
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原文地址：https://www.cnblogs.com/xingnie/p/15237818.html