Re: [PATCH] Implement fast hash-collision detection

Nguyen Thai Ngoc Duy [off-list ref] writes:

What I'm thinking is whether it's possible to decouple two sha-1 roles
in git, as object identifier and digest, separately.

Why it would be a good thing? If you have a collided identifier, somebody
has to choose which blob a particular tree wants to have at the path, and
because the tree would not record anything but the identifier, you cannot.

...
The day sha-1 is broken, a project can generate new digests from its
old good repo and enforce developers to use new digests for
verification instead of sha-1. sha-1 is still used by git as
identifier after that day.

And an old blob that is identified with a SHA-1 now has a new blob that
has different contents but happens to have the same SHA-1. How does Git
decide which blob to use when a particular object is named by the SHA-1?