In big projects it is best practice to outsource functionality into single packages to share them between different projects. It will work great, until changes have to be implemented across different packages or they where sliced suboptimal. When those packages or projects - wich will mostly be handled in their own repositories - merged together into one repository, we’re taking about a MonoRepo or also Multi-Package-Repository.
LernaJS is a command-line based tool, that can enormously simplify the administrative tasks in such a structure: creating pre-releases, versioning, linking packages within the MonoRepos and publishing the changed packages. So just import all the individual repositories and off you go!
But is it as easy as it seems? I will show you with the help of a step-by-step-list for the migration of multiple repositories in a MonoRepo and which pitfalls you will reach during the migration.