670,000 commits. Thats big. But only 2K merges? I assume push straight to master in most cases?
I don't think either SCCS or RCS tracked merges, so everything looks like a new revision.
Many folks nowadays don't get how lucky they are, not having to do UNIX development on a time-sharing system, although cloud systems kind of replicate the experience.
Good for simple stateless services (web servers, API endpoints, microservices) applications that fit the unikernel model - single-purpose, statically linked Running on one's own Xen hypervisor infrastructure.
https://www-old.cs.utah.edu/flux/oskit/