Its possible to go in and replace the hash algorithm with something else, which none of these "git is going to ruin everything with not replacing SHA1 this instant!" people seem to bother with, to prove their points, instead of endless posturing.

http://stackoverflow.com/a/34599081 has actually gone about doing it, but it has been over a year since that, and as linus says, there has been multiple collision mitigations added as well, so tests should probably be re-done