code: func (f Formation) Merge(other Formation) Formation {
  	new := make(Formation)
  
  	for name, p := range f {
  		if existing, found := other[name]; found {
  			// If the existing Formation already had a process
  			// configuration for this process type, copy over the
  			// instance count.
  			p.Quantity = existing.Quantity
  			p.SetConstraints(existing.Constraints())
  		} else {
  			p.Quantity = DefaultQuantities[name]
  			p.SetConstraints(DefaultConstraints)
  		}
  
  		new[name] = p
  	}
  
  	return new
  }
docs: // Merge merges in the existing quantity and constraints from the old Formation
  // into this Formation.