Usually, the notices want a public repository to be closed by Github. The guilty repo owner has just 24 hours to make the necessary or the repo is closed, which is very short : I saw very few repos updated that much.
So, why not make a backup of the repo during this gap ?
Using Github API ? https://developer.github.com/v3/repos/commits/
Here are some trails to begin with :
https://api.github.com/repos/github/dmca https://api.github.com/repos/github/dmca/commits https://api.github.com/repos/github/dmca/git/trees/bbddacc1cb3d1fdfa64aa72b64270c0df2af38f3
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