Why does git:// works but git@ does not

Question

Why does git:// works

$ git clone git://github.com/schacon/grit.git
Cloning into \'grit\'...
...
Checking connectivity... done.

but git@ do

Answer 1

This is because git@ uses ssh protocol. It is equivalent to ssh://git@.. So if you dont have correct ssh keys it will not work. Option git:// however uses git protocol which is similar to ssh but uses no authentication at all. See chapter on protocols for more information.