gh-mirror is a simple way to mirror a user's GitHub repositories locally, maintaining the upstream repository metadata, and keep them updated easily. See the blog post I wrote it for to get more information about how to use it in a useful way.
$ gh-mirror cdown
Cloning into bare repository 'Apache-ETag.git'...
remote: Counting objects: 7, done.
remote: Compressing objects: 100% (5/5), done.
remote: Total 7 (delta 0), reused 6 (delta 0)
Receiving objects: 100% (7/7), done.
Checking connectivity... done.
Cloning into bare repository 'bats.git'...
[...]
gh-mirror is ISC licensed. See the LICENSE file for full details.