Re: SHA1 collisions found

Hi Junio,

On Fri, Feb 24, 2017 at 10:10:01PM -0800, Junio C Hamano wrote:

I was thinking we would need mixed mode support for smoother
transition, but it now seems to me that the approach to stratify the
history into old and new is workable.

As someone looking to deploy (and having previously deployed) git in
unconventional roles, I'd like to add one caveat.  The flag day in the
history is great, but I'd like to be able to confirm the integrity of
the old history.

"Counter-hashing" the blobs is easy enough, but the trees, commits and
tags would need to have, iiuc, some sort of cross-reference.  As in my
previous example, "git tag -v v3.16" also checks the counter hash to
further verify the integrity of the history (yes, it *really* needs to
check all of the old hashes, but I'd like to make sure I can do step one
first).

Would there be opposition to counter-hashing the old commits at the flag
day?

thx,

Jason.