Current Human Moral Code: I will shoot my foot for you. Instead you shoot your foot for me. Whoever stops shooting first is an selfish bastard because he cares about his own foot more than his neighbour's.
What's that?.. you care more about your foot? That is disgusting! People ought to shoot themselves in their foot more. We are in a age of moral crisis where no one seems to want to shoot their own foot for the other's sake. What kind of hell is this world coming too?! \sarcasm..
Christian Moral Code: You ought to keep shooting in your foot for others even if others don't do the same for you. If you don't you will rot in hell. Psst.. you don't have to really shoot in your foot for others. Just pretend that you do. And you will get brownie points in return.
Objectivist Moral Code: Stop shooting feet. You have the right to exist without shooting your own feet. Do some thing productive. Exchange your produce with others who have what you want and you have what they want. Give your produce away for free when you feel like. Let no one coerce you to be compassionate.