I did exactly that at work, when I inherited maintainership of a legacy internal software program, which until then has been developed with the same "version co

I did exactly that at work, when I inherited maintainership of a legacy internal software program, which until then has been developed with the same "version control" approach as DF - a folder/zipfile per release or per feature branch. As a bonus, it is something that has to run on three different operating systems, and the source code for each has been kept separately, and synced manually every now and then. Granted, it was only like a dozen or so releases and not 20 years worth of development like DF, but that's just a matter of scale, not of principle. :)