Re: [PATCH 10/10] Enable SHA-256 by default in breaking changes mode

From: Junio C Hamano <gitster@pobox.com>
Date: Jun 20, 2025, 15:03 UTC
Message-ID: <xmqqfrfu5ubo.fsf@gitster.g>
In-Reply-To: <20250620011943.586596-11-sandals@crustytoothpaste.net>

"brian m. carlson" <sandals@crustytoothpaste.net> writes:

Show 7 quoted lines

> Our document on breaking changes indicates that we intend to default to
> SHA-256 in Git 3.0.  Since most people choose the default option, this
> is an important security upgrade to our defaults.
>
> To allow people to test this case, when WITH_BREAKING_CHANGES is set in
> the configuration, build Git with SHA-256 as the default hash.  Update
> the testsuite to reflect this configuration so that the tests pass.

Another thing that I suspect nobody wrote tests for, but we must be absolutely certain, is that the post-3.0 Git can still interoperate well with historical SHA-1 repositories (I am not talking about "fetch from SHA-1 into SHA-256", but "the binary does not lose ability to work in SHA-1 repositories or fetch/push between SHA-1 repositories, only because the default is set to SHA-256"), even in old repositories people have been using for ages without the core.repositoryformatversion defined.

Thanks.