This was way harder than it needs to be, because MacOS X Lion ships with git 18.104.22.168 in /usr/bin. Here’s a quick sequence of steps:
- Download and install latest version from http://git-scm.com/. This appears to work but won’t change anything from the command line. The new version is installed in /usr/local/git.
- Reconfigure your path to put /usr/local/git/bin in front of /usr/bin. Something like this in your ~/.bash_profile: