https://tonym.us/migrating-monorepo-microservices.html
Migrating to a Monorepo from Microservices with Git Subtree // Tony Metzidis
git subtreemigratingmonorepo
https://git.code-maven.com/git/git/extra/git-subtree-change-subtree
git subtree change in subtree - Git
git subtreechange
https://www.subtreesplit.com/
Git Subtree Split as a Service
A service for easily set up web hooks and deploy keys for using git subtree split. Split your monorepo into many repos to ease maintenance of your oranisation.
git subtreesplitservice
https://docs.github.com/de/enterprise-server@3.6/get-started/using-git/about-git-subtree-merges
About Git subtree merges - GitHub Enterprise Server 3.6 Docs
If you need to manage multiple projects within a single repository, you can use a subtree merge to handle all the references.
github enterprise serversubtreemergesdocs