TL;DR

Symlinks provides an easy to construct a sourceDir that that references select parts of a larger repository.

Design

If one wants to share code among a couple of cloud functions in a repo, then symlinking in a shared folder would be an easy way to achieve that.

References

#36: An opt out approach to assuring the right content gets uploaded rather than this opt in approach. (And #65 which fixes that I one and might make this one easier to solve)