I was using Git on a Windows box and the git bash always used the web version for help. I really liked this and I am trying to do the same on my mac.
I ran:
I'm not an OS X user, but I suppose that the shell doesn't let you pass a multi-word argument without escaping it.
Edit directly your ~/.gitconfig file and insert the following [web] section:
~/.gitconfig
[web]
[web] browser = open -a Firefox.app