You can usually get any air out of the top end of the system, which is where it’ll be if you’re just shortening the hose, by moving the lever back and forth with the reservoir top off – top up if needed – and/or zip-tieing the lever back to the bars and leaving overnight. If you think about it, there’s no reason for air to have got into the caliper end of the system, so a full bleed shouldn’t really be needed.
Coincidentally I did exactly this last night on a mate’s bike and it was fine – XT brakes, changed levers, no bleeding needed, just some waggling. Oh, and the little yellow blocks that come with Shimano hose kits are a big help, clamp them around the hose in a vice or some adjustable grips and tap the pin thing in with a hammer. Don’s forget to slide the plastic bolt cover, the hollow bolt and the olive onto the hose first in that order and the right way up first 🙂