[ we make science jokes, periodically ]

Why spend time gathering sticks, flints and feathers when you can code infinity arrows? When you shoot one, another falls from the sky! Ready? Let's go! 

Step 1 
Delete the on start and on chat command blocks.

Step 2
Add an on arrow shot block.
Now add a spawn block inside the on arrow shot block.
Change the position parameter to read ~0 ~3 ~0

Here's something on parameters:

Step 3

Replace the chicken egg with projectile and change it to an arrow.

BOOM! Infinity arrows! How awesome is that?