How to collaborate with multiple npm publishers on one module

How can we organize our file-system and processes if there are multiple publishers on an npm module? Do we need a common repository (ex. GIT) or is there a smart way to use npm's own publishing & updating process?

The main issue I can't get my head around is that the initial publisher of the package is not able to get the latest version from within the package itself, is he? Unless he installs it as a dependency on another package and then updates & publishes from within that dependency.