code: func (c *Commit) File(path string) (*File, error) {
  	tree, err := c.Tree()
  	if err != nil {
  		return nil, err
  	}
  
  	return tree.File(path)
  }
docs: // File returns the file with the specified "path" in the commit and a
  // nil error if the file exists. If the file does not exist, it returns
  // a nil file and the ErrFileNotFound error.