[$] A new hash algorithm for Git

The Git source-code management system is famously built on the SHA‑1
hashing algorithm,
which has become an increasingly weak foundation over the years. SHA‑1 is
now considered to be broken and, despite the fact that it does not yet seem
to be so broken that it could be used to compromise Git repositories, users
are increasingly worried about its security. The good news is that work on
moving Git past SHA‑1 has been underway for some time, and is slowly
coming to fruition; there is a version of the code that can be looked at
now.