The Common Paper app[1], though not quite a git workflow, has always struck me as being pretty close to how an software engineer might approach contracts:
1. An immutable set of standard terms, with variable references.
2. A collection of cover page variables, that modify the standard terms by reference.
3. A structured negotiation workflow, where users "propose changes" to the cover page variables with automatic "diff-ing" (redlining).
It's not a product targeted to software engineers, but has always appealed to me as a way to sneak in some engineering best-practices into the world of lawyering :)
Full disclosure: I'm an employee