code: func (p DestinationPublisher) Publish(d Descriptor) error {
  	if d.TargetPath == "" {
  		return errors.New("Publish: must provide a TargetPath")
  	}
  
  	src := d.Src
  
  	transformers := p.createTransformerChain(d)
  
  	if len(transformers) != 0 {
  		b := bp.GetBuffer()
  		defer bp.PutBuffer(b)
  
  		if err := transformers.Apply(b, d.Src); err != nil {
  			return err
  		}
  
  		// This is now what we write to disk.
  		src = b
  	}
  
  	f, err := helpers.OpenFileForWriting(p.fs, d.TargetPath)
  	if err != nil {
  		return err
  	}
  	defer f.Close()
  
  	_, err = io.Copy(f, src)
  	if err == nil && d.StatCounter != nil {
  		atomic.AddUint64(d.StatCounter, uint64(1))
  	}
  	return err
  }
docs: // Publish applies any relevant transformations and writes the file
  // to its destination, e.g. /public.