Migrate from Bitbucket to GitHub

Check out the existing repository from Bitbucket

git clone https://[email protected]/USER/PROJECT.git

Add the new Github repository as upstream remote of the repository checked out from Bitbucket

cd PROJECT
git remote add upstream https://github.com:USER/PROJECT.git

Push all branches

git push upstream master
git push --tags upstream

References
https://medium.com/@RobertKhou/how-to-migrate-from-bitbucket-to-github-75c87a892767