1) Go to https://api.github.com/repos/<USER>/<REPO>
2) Check the `size` property
Example: https://api.github.com/repos/torvalds/linux
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Shell command: echo https://github.com/torvalds/linux.git | perl -ne 'print $1 if m!([^/]+/[^/]+?)(?:.git)?$!' | xargs -I{} curl -s -k https://api.github.com/repos/'{}' | grep size
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