Assume we have monorepo at git@github.com/haydenk/monorepo.git

With directory contents:

packageA/
packageB/
packageC/

I did say simple

1. Create the new repository. git@github.com/haydenk/packageA.git
2. Clone the repository into an appropriate name for the new repository.
   • git clone git@github.com/haydenk/monorepo.git packageA/
3. Replace the origin remote with the new repository.
   • git remote remove origin
   • git remote add origin git@github.com/haydenk/packageA.git
4. Rewrite the repository to only the subdirectory or subdirectories you want in the new repository. With either master or develop branch or whatever branch you want to use.
   • git filter-branch --prune-empty --subdirectory-filter packageA -- develop
   • I chose develop because I will create a release branch to push this to master or you can simply merge into master.
5. Push the rewrites
   • git push --all
   • git push --tags