laravel/homestead をインストールし、「composer update」を試しました。Composer から、プライベート リポジトリに関する TransportException が返されます。
Composer update
Loading composer repositories with package information
Your GitHub credentials are required to fetch private repository metadata (https://github.com/GrahamCampbell/asset)
A token will be created and stored in "/home/vagrant/.composer/auth.json", your password will never be stored
To revoke access to this token you can visit https://github.com/settings/applications
Username:
Password:
Token successfully created
[Composer\Downloader\TransportException]
The "https://api.github.com/repos/GrahamCampbell/asset" file could not be downloaded (HTTP/1.1 404 Not Found)
このポイントを通過できないので、立ち往生しています。