I just upgraded my Mac from Lion to Mountain Lion this morning. I must say the Mac OS just keeps getting better :). After the upgrade I just noticed that git was broken and I was getting the Command not found error.

To fix this : * Download the latest git package from here. * If you try and install the package directly, it will fail to install and would complain saying Unidentified source. This is due to the new Gatekeeper feature in Mountain Lion. To fix this go to System Preferences -> Security & Privacy and select Anywhere under Allow Applications Downloaded from section. * Go ahead and install the package you just downloaded.

An alternative method to fix this can be found here.