You can see it's broken across the weakest point, in the nut slot. I stripped the guitar down and clamped it to my bench, on a sash cramp. I made a fixture to keep the headstock in the right inclination, and was then able to bring the headstock to the neck with controlled clamping force.
Glue set, it was then a matter of repairing the finish.
Not completely invisible, but it's been playing again for more than 3 years now.