This metal pole in the backyard

I'd probably try for a mix of natural light, fluorescent, and point lights.

The natural light will be the most economical, but obviously fails at night.

The fluorescent lighting should give you enough light for most working conditions.

And the point lights should help for when you need to do detail work or get under the hood of your cars. You can find point lights on articulated arms, that way you can just grab and move the light to wherever you need it. Mounting an arm or two on each pole would probably be enough.

You said that one end is attached to the house, and the other end is attached to a post which is attached to a vehicle shed.

Is there any reason why you need a post on the vehicle shed end? Could you attach the line directly to the shed (e.g. with an eye-bolt)? That would seem like the simplest solution.

ETA: Given the slope of the land, maybe a metal post attached to the side of the shed would be a good option? Something similar to what you might use for a lamp post?