When I ran git gui
, I got this:
$ git gui
git: \'gui\' is not a git command. See \'git --help\'.
Did you mean one of these?
grep
init
p
While I am not sure how to open git gui from the terminal in Mountain Lion it is possible to use it using OpenInGitGUI which opens git gui from Finder. The download and instructions are available here.
This may not be quite as convenient as typing 'git gui' in the terminal but it is pretty close. Basically all you need to do is type 'open .' to open the current directory in Finder and then click the Git button to open up git gui.