> git as-is is completely unfit for purpose and a huge security risk for this use case, because it uses MD5, which is no longer collision-resistant.

Firstly, git does not use MD5. It uses SHA1.

Secondly, since 2017 git has shipped with an implementation of SHA1 (sha1dc) that detects the collision attack you describe, which for this use case renders it a non-issue.

Thirdly, git supports `git init --object-format=sha256` which removes the whole issue for anyone who cares to do so.

I think git as-is solves the problem nicely. The only additional value blockchain provides is the ability for someone to point at it and say "look! A use for blockchain exists!" which isn't worth the downsides it'll bring.