> re-factoring a big repo of decades old fortran+C cod

Having been in academia in the past and now in software I can say with a lot of certainty that this will take a lot more upfront work than otherwise.

Academic code does not have a lot of structure. And usually lacks a lot in terms of tests. While AI is best when it can mimic patterns as well as there are tests to target.

So you will probably need to budget a few weeks to establish good patters, docs as well as testing patterns before you can seriously make it really do what you want it to do.

exactly yeah it was a code base written by atmospheric physicists I assume and I had an idea that maybe copilot could get it working to interface with some more modern software and it just didn't really have what it takes.

Even with 3 weeks I'm just not the Fortran/C programmer to get that job done so I moved on to other things.