code: func (s *MigrationService) MapCommitAuthor(ctx context.Context, owner, repo string, id int64, author *SourceImportAuthor) (*SourceImportAuthor, *Response, error) {
  	u := fmt.Sprintf("repos/%v/%v/import/authors/%v", owner, repo, id)
  	req, err := s.client.NewRequest("PATCH", u, author)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	// TODO: remove custom Accept header when this API fully launches
  	req.Header.Set("Accept", mediaTypeImportPreview)
  
  	out := new(SourceImportAuthor)
  	resp, err := s.client.Do(ctx, req, out)
  	if err != nil {
  		return nil, resp, err
  	}
  
  	return out, resp, nil
  }
docs: // MapCommitAuthor updates an author's identity for the import. Your
  // application can continue updating authors any time before you push new
  // commits to the repository.
  //
  // GitHub API docs: https://developer.github.com/v3/migration/source_imports/#map-a-commit-author