> The first thing that you'll notice (other than the much longer hash value) is that you can't push this code to GitHub, though that will almost certainly be fixed by the time Git 3.0 is released. In fact, that's probably the main thing currently delaying 3.0 entirely.

> But when you do want to push it to GitHub (or any host), you will need to tell them when creating the repository on the server that this is a sha256 project. Every project will now be in one bucket or the other and they cannot be mixed.

> This is immediately going to frustrate people because now they need to know what version of git they ran git init with and make sure when they go to GitHub to create the server repository, they choose the right one.

Github can fix this problem, and we have had siilar stuff in the past, when we had to switch repos. This is simple and doable, just need gradual work. I don't see the problem.