I had a 12 mile commute then I was teaching in atlanta. All I took with me were tools to remove the wheel, levers, tube, CO2 and a patch kit. All the other crap is stuff you pick up if you decide you need it. Depending on the availability of public transit, I take more or less. If I'm in the middle of nowhere I'll add another tube and a minipump just in case.

Worst case, 12 miles is walkable.