I ran into an interesting problem recently after updating my installation of Homebrew on my Mac Pro. ? Starting with the update command, which ran successfully:

$ brew update

I then attempted to update my redis installation to the latest:

$ brew upgrade redis

I was greeted with this message:

Error: undefined local variable or method `brew_install' for main:Object

Trying several things on my own to no avail, led me to a Google search result pointing out a known issue and solution. ?It appears there is an issue with a brew_upgrade.rb artifact being left behind after a brew update. ?The following commands from the Homebrew wiki fix the problem:

$ cd $(brew --prefix)/Library/Contributions/examples
$ git clean -n # if this doesn't list anything that you want to keep, then
$ git clean -f # this will remove untracked files

I hope this helps someone with the same problem.