Re: [PATCH 2/2] diff: teach diff to read gitattribute diff-algorithm

> It can be useful to specify diff algorithms per file type. For example,
> one may want to use the minimal diff algorithm for .json files, another
> for .c files, etc.
>
> Teach the diff machinery to check attributes for a diff algorithm.
> Enforce precedence by favoring the command line option, then looking at
> attributes, then finally the config.
>
> To enforce precedence order, set the `xdl_opts_command_line` member
> during options pasing to indicate the diff algorithm was set via command
> line args.
>
> Signed-off-by: John Cai <johncai86@gmail.com>
> ---
> diff --git a/diff.c b/diff.c
> @@ -3652,6 +3652,27 @@ static void builtin_diff(const char *name_a,
> +               if (!o->xdl_opts_command_line) {
> +                       static struct attr_check *check;

> +                       attr_check_append(check, git_attr("diff-algorithm"));
> +
> +                       git_check_attr(the_repository->index, NULL, one->path, check);
> +                       one_diff_algo = check->items[0].value;
> +                       git_check_attr(the_repository->index, NULL, two->path, check);
> +                       two_diff_algo = check->items[0].value;
> +
> +                       if (!ATTR_UNSET(one_diff_algo) && !ATTR_UNSET(two_diff_algo) &&
> +                               !strcmp(one_diff_algo, two_diff_algo))
> +                               set_diff_algorithm(o, one_diff_algo);
> +
> +                       attr_check_free(check);