解决方法

第一步

执行brew update --verbose

% brew update -verbose
Checking if we need to fetch /opt/homebrew...
Checking if we need to fetch /opt/homebrew/Library/Taps/homebrew/homebrew-cask...
Fetching /opt/homebrew...
Checking if we need to fetch /opt/homebrew/Library/Taps/homebrew/homebrew-core...
Fetching /opt/homebrew/Library/Taps/homebrew/homebrew-core...
Fetching /opt/homebrew/Library/Taps/homebrew/homebrew-cask...
fatal: unable to access 'https://github.com/Homebrew/homebrew-cask/': Failed to connect to github.com port 443: Operation timed out
Error: Fetching /opt/homebrew/Library/Taps/homebrew/homebrew-cask failed!
Updating /opt/homebrew...
Branch 'master' set up to track remote branch 'master' from 'origin'.
Switched to and reset branch 'master'
Your branch is up to date with 'origin/master'.
Switched to and reset branch 'stable'
Current branch stable is up to date.

Updating /opt/homebrew/Library/Taps/homebrew/homebrew-core...
fatal: Could not resolve HEAD to a revision

第二步：解决报错

cd /opt/homebrew/Library/Taps/homebrew/homebrew-core
git fetch --prune origin
git pull --rebase origin master

第三步：再次更新

brew update