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.