Using impulse force to rotate a Rigidbody2D to desired rotation.

I'm putting this one up because a few people have asked this online but they didn't really get a decent answer.

One night I my ended up struggling on this normally simple problem, at a time of day when I'm not my sharpest (that's my excuse and I'm sticking by it!).

You see there's a Gotcha with Unity which I was too tired to spot until I found a forum post pointing out this inconsistency. Rather than sticking with one, Rigidbody2D's variables and functions work in a mix of degrees and radians. So I spent ages jamming degrees in AddTorque wondering why the hell it wasn't working.

Anyway here's what I got! I hope you find this useful.

float currentRot = m_RB.rotation;
float turn = -((((currentRot + 180f) % 360f + 360f) % 360f) - 180f); // Work out the shortest way to turn to 0 degrees
float angularVelocity = turn / (Time.deltaTime * 4f); // Remove the *4f if you want to snap to target angle
float deltaVelocity = (angularVelocity - m_RB.angularVelocity) * Mathf.Deg2Rad;

m_RB.AddTorque(m_RB.inertia * deltaVelocity, ForceMode2D.Impulse);