Add a version check to git for the version being used in git_utils.py

Not sure if this is a bug or not. I am successfully using the fsurdat modifier tool on the cheyenne log-in node, but when I try to use it on casper, I get the following error


However, now that when I've now run it successfully on cheyenne and I then try to run it on casper, I no longer get the error. Is this because in the first time the tool is used it is trying to grab something from the internet (through the calls to git in the error) and casper is not connected to the outside world, while cheyenne is?

If so, it's perhaps not a problem, but I'm working on documentation and it would be good to make people aware of this if it's something they will experience.