code: func (s *ChangesService) GetContentType(changeID, revisionID, fileID string) (*Response, error) {
  	u := fmt.Sprintf("changes/%s/revisions/%s/files/%s/content", changeID, revisionID, url.PathEscape(fileID))
  
  	req, err := s.client.NewRequest("HEAD", u, nil)
  	if err != nil {
  		return nil, err
  	}
  
  	return s.client.Do(req, nil)
  }
docs: // GetContentType gets the content type of a file from a certain revision.
  // This is nearly the same as GetContent.
  // But if only the content type is required, callers should use HEAD to avoid downloading the encoded file contents.
  //
  // For further documentation see GetContent.
  //
  // Gerrit API docs: https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#get-content