code: func Copy(ctx context.Context, c *cli.Context, store storer) error {
  	from := c.Args().Get(0)
  	to := c.Args().Get(1)
  
  	// argument checking is in s.binaryCopy
  	if err := binaryCopy(ctx, c, from, to, false, store); err != nil {
  		return action.ExitError(ctx, action.ExitUnknown, err, "%s", err)
  	}
  	return nil
  }
docs: // Copy copies either from the filesystem to the store or from the store
  // to the filesystem