code: func (p *Package) File(name, src string) {
  	if p.err != nil {
  		return
  	}
  
  	f, err := os.Open(src)
  	if err != nil {
  		p.err = err
  		return
  	}
  	defer f.Close()
  	p.Copy(name, f)
  }
docs: // File writes a file to the push package.
  //
  // NOTE: Name is a relative path. Only forward slashes are allowed.