Re: [PATCH 1/2] alter hash function: expose test dependencies on sha1

[Junio C Hamano <gitster@pobox.com>]

Stefan Beller <sbeller@google.com> writes:

> DO NOT APPLY.
>
> Alter the hash function such that with this patch
> any dependency on sha1 in tests will make the test
> fail. This patch applied on master yields this list:
>
> ./t0000-basic.sh
> ....
> ./t8008-blame-formats.sh
>
> Signed-off-by: Stefan Beller <sbeller@google.com>
> ---
>  sha1dc/sha1.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Everybody knew and said that we need to make tests less dependent on
the exact hash and in such a way that the ones that currently do
would test the morally equivalent thing with a new hash before we
can go forward.  And everybody said that one way to start that is to
build a Git with different hash function and trying to run tests.

This is the first report of doing so, and the large list above is
the biggest contribution this message makes to the "let's wean
ourselves off of SHA-1" journey.

Thanks for starting this.

>
> diff --git a/sha1dc/sha1.c b/sha1dc/sha1.c
> index 25eded1399..e18acee9ca 100644
> --- a/sha1dc/sha1.c
> +++ b/sha1dc/sha1.c
> @@ -1756,7 +1756,7 @@ static void sha1_process(SHA1_CTX* ctx, const uint32_t block[16])
>  void SHA1DCInit(SHA1_CTX* ctx)
>  {
>  	ctx->total = 0;
> -	ctx->ihv[0] = 0x67452301;
> +	ctx->ihv[0] = 0x07452301;
>  	ctx->ihv[1] = 0xEFCDAB89;
>  	ctx->ihv[2] = 0x98BADCFE;
>  	ctx->ihv[3] = 0x10325476;