2020 年 12 月以降に Homebrew で brew update をしようとすると次のようなエラーが出て処理が実行できないことがあります。 Error: homebrew-core is a shallow clone. To `brew update` first run: git -C "/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core" fetch --unshallow This restriction has been made on GitHub's request because updating shallow clones is an extremely expensive operation due to the tree layout and traffic of Homebrew/homebre