Homebrew is a very convenient package manager for Mac OS X. It makes the installation of numerous utilities and programs incredibly easy. It is based on a databases of instructions (Ruby formulas) that are kept up to date using Git.
Keeping the database up-to-date is normally done with
brew update
Sometimes, however, it can fail. It occurred to me already a few times that I was unable to retrieve the latest version of the database, and installing new software becomes impossible.
If the internal diagnostic tool
brew doctor
is not sufficient for identifying and solving the issue, there is a way to force the update. As indicated on these pages, one can use Git directly and recover the database:
cd `brew --prefix`
git remote add origin https://github.com/mxcl/homebrew.git
git fetch origin
git reset --hard origin/master
Francesco Turci 