code: func (c *Client) GetDiff(i *GetDiffInput) (*Diff, error) {
  	if i.Service == "" {
  		return nil, ErrMissingService
  	}
  
  	if i.From == 0 {
  		return nil, ErrMissingFrom
  	}
  
  	if i.To == 0 {
  		return nil, ErrMissingTo
  	}
  
  	path := fmt.Sprintf("service/%s/diff/from/%d/to/%d", i.Service, i.From, i.To)
  	resp, err := c.Get(path, nil)
  	if err != nil {
  		return nil, err
  	}
  
  	var d *Diff
  	if err := decodeJSON(&d, resp.Body); err != nil {
  		return nil, err
  	}
  	return d, nil
  }
docs: // GetDiff returns the diff of the given versions.