message: Ensure arrayHasDiff returns a boolean
  This is just maintenance noticed while debugging.
diff: @@ -53,6 +53,9 @@ export function arrayHasDiff(a: any[], b: any[]): boolean {
  // an element from the other.
  if (b.some(i => !a.includes(i))) return true;
  if (a.some(i => !b.includes(i))) return true;
  +
  + // if all the keys are common, say so
  + return false
  } else {
  return true; // different lengths means they are naturally diverged
  }
  