Subject: Re: [PATCH] hash binary sha1 into patch id

From: Jonathan Nieder <[email-masked]>
Date: Fri, 13 Aug 2010 15:00:31 -0500

Clemens Buchacher wrote:

> Since commit 2f82f760 (Take binary diffs into account for "git rebase"), binary
> files are included in patch ID computation. Binary files are diffed using the
> text diff algorithm, however
[...]
> Instead of hashing the diff of binary files, use the post-image sha1, which is
> just as unique. As a result, performance is much improved.

Maybe it should use both the pre- and post-image?

> diff --git a/diff.c b/diff.c
> index 17873f3..20fc6db 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -3758,6 +3758,12 @@ static int diff_get_patch_id(struct diff_options *options, unsigned char *sha1)
>  					len2, p->two->path);
>  		git_SHA1_Update(&ctx, buffer, len1);
>  
> +		if (diff_filespec_is_binary(p->two)) {
> +			len1 = sprintf(buffer, "%s", sha1_to_hex(p->two->sha1));
> +			git_SHA1_Update(&ctx, buffer, len1);

i.e., maybe also

			git_SHA1_Update(&ctx, sha1_to_hex(p->one->sha1), 40);

Luckily this is after the filenames and so on have been incorporated,
so there’s no need to add that specially.