Error: homebrew-core is a shallow clone. homebrew-cask is a shallow clone. To `brew update`, first run: git -C /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core fetch --unshallow git -C /usr/local/Homebrew/Library/Taps/homebrew/homebrew-cask 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/homebrew-core and Homebrew/homebrew-cask. We don't do this for you automatically to avoid repeatedly performing an expensive unshallow operation in CI systems (which should instead be fixed to not use shallow clones). Sorry for the inconvenience!
めちゃめちゃ時間かかった (ズンビーになったかと思った) ので時間あるときにやるといいすよ。