In lerna you can restrict versioning to a particular branch. So you check out your feature branch, work until it's ready to share and then merge it back into master and create a version.

Creating a version tags the commit with the version number for each package that's been updated and it allows for the creation of pre-release versions. If you have things that aren't ready for prime time.

Consumers can depend on a particular git commit by referencing the tag.

So there is one main branch that contains all of the commits, but different components are versioned independently and reference particular commits in the branch.