Consider the improvements regarding support for SHA-256 in Git, last mentioned in the release notes for version 2.45:

• https://github.com/git/git/blob/master/Documentation/RelNotes/2.45.0.txt
• https://github.blog/open-source/git/highlights-from-git-2-45/

libgit2 has experimental support for SHA-256, guarded by -DEXPERIMENTAL_SHA256.

There is a reference to this in git2-rs:

It might be useful to allow users explore SHA-256 compatibility with git2-rs, probably behind a feature flag.