[git] How do I update Homebrew?

When I ran:

brew update

I got a message saying it initialized an empty repository in /usr/local/.git/, then I got this error:

Alternatively you could update brew by installing it again. (Think I did this as El Capitan changed something)

Note: this is a heavy handed approach that will remove all applications installed via brew!

Try to install brew a fresh and it will tell how to uninstall.

At original time of writing to uninstall:

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall)"

Edit: As of 2020 to uninstall:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall.sh)"

• cd /usr/local
• git status
• Discard all the changes (unless you actually want to try to commit to Homebrew - you probably don't)
• git status til it's clean
• brew update