Mirroring a repository
Create a bare clone of the repository.
git clone --bare https://github.com/exampleuser/old-repository.git
Mirror-push to the new repository.
cd old-repository.git
git push --mirror https://github.com/exampleuser/new-repository.git
Remove the temporary local repository you created in step 1.
cd ..
rm -rf old-repository.git
Mirroring a repository that contains Git Large File Storage objects
Create a bare clone of the repository. Replace the example username with the name of the person or organization who owns the repository, and replace the example repository name with the name of the repository you'd like to duplicate.
git clone --bare https://github.com/exampleuser/old-repository.git
Navigate to the repository you just cloned.
cd old-repository.git
Pull in the repository's Git Large File Storage objects.
git lfs fetch --all
Mirror-push to the new repository.
git push --mirror https://github.com/exampleuser/new-repository.git
Push the repository's Git Large File Storage objects to your mirror.
git lfs push --all https://github.com/exampleuser/new-repository.git
Remove the temporary local repository you created in step 1.
cd ..
rm -rf old-repository.git
Above instruction comes from Github Help: https://help.github.com/articles/duplicating-a-repository/