> woefully confused

Yes, I didn't understand that the GPG signing just operates on the top level object in the commit and trusts the SHA-1 hashes contained in it.

The signing process doesn't recursively traverse the bytes of the commit to pull them into GPG, like you would expect.

It's like, imagine you made a "bill of materials" of your project's files consisting of their names and CRC-32 checksums, and then signed this file, and called your project securely signed, LOL.

This aspect can be fixed without foisting new hashing scheme into the content tracker. In fact, it must be fixed; users on SHA-1-based repos deserve secure signing.

It's really sneaky that the SHA-1 business (not intended to be a security mechanism) was embroiled into the signing implementation; that GPG is demoted to the strength of SHA-1.

Was that just to save some cycles? It's certainly faster just to sign the commit object!

signatures are basically always computed over hashes. The only problem here is that the hashes are not secure. And this is being fixed.