Give another go at force removing the brewed version of git
brew uninstall --force git
Then cleanup any older versions and clear the brew cache
brew cleanup -s git
Remove any dead symlinks
brew cleanup --prune-prefix
Then try reinstalling git
brew install git
If that doesn’t work, I’d remove that installation of Homebrew altogether and reinstall it. If you haven’t placed anything else in your brew --prefix directory (/usr/local by default), you can simply rm -rf $(brew --prefix). Otherwise the Homebrew wiki recommends using a script at https://gist.github.com/mxcl/1173223#file-uninstall_homebrew-sh