执行brew update后显示Permission denied

执行brew update后显示如下：

touch: /usr/local/.git/FETCH_HEAD: Permission denied
error: cannot open .git/FETCH_HEAD: Permission denied

/usr/local/Library/Homebrew/cmd/update.sh: line 514: /usr/local/.git/UPDATE_FAILED: Permission denied
touch: /usr/local/Library/Taps/homebrew/homebrew-nginx/.git/FETCH_HEAD: Permission denied
error: cannot open .git/FETCH_HEAD: Permission denied

/usr/local/Library/Homebrew/cmd/update.sh: line 514: /usr/local/.git/UPDATE_FAILED: Permission denied
==> Homebrew has enabled anonymous aggregate user behaviour analytics.
Read the analytics documentation (and how to opt-out) here:
  http://docs.brew.sh/Analytics.html

error: could not lock config file .git/config: Permission denied
Error: Failure while executing: git config --local --replace-all homebrew.analyticsmessage true

解决办法：

执行以下命令即可解决问题

sudo chown -R $(whoami) /usr/local