Brew tool - "fatal: could not resolve head to a revision" error resolution

  Problem description ：

It's going on brew update when , An error occurred , as follows ：

% brew update

fatal: Could not resolve HEAD to a revision

Already up-to-date.

terms of settlement ：

Ideas ：

1） Error found homebrew The catalog of ;

2） Go to the directory , perform fetch and  pull command .

1） function “brew update --verbose”, Error found homebrew The catalog of ：

% brew update --verbose

Checking if we need to fetch /usr/local/Homebrew...

Checking if we need to fetch /usr/local/Homebrew/Library/Taps/homebrew/homebrew-cask...

Checking if we need to fetch /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core...

Fetching /usr/local/Homebrew...

Updating /usr/local/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 /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core...

fatal: Could not resolve HEAD to a revision

Already up-to-date.

2） Go to the wrong directory , And then first fetch, after pull, as follows ：

cd /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core

% pwd

/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core

% git fetch --prune origin

% git pull --rebase origin master

 From https://github.com/Homebrew/homebrew-core

* branch                    master     -> FETCH_HEAD

Updating files: 100% (6435/6435), done.

Here's the picture ：

 

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