Re: Regression in `git diff --quiet HEAD` when a new file is staged

> Looking at that patch, my biggest concern is: are we missing other spots
> that need to special-case the dry_run setting? Because it's a regression
> in a maint release, I'm tempted to say we should do the dumbest possible
> thing that covers all cases and just revert this hunk from the original
> patch, like:
>
> diff --git a/diff.c b/diff.c
> index 87fa16b730..687206f353 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -6890,6 +6890,15 @@ void diff_flush(struct diff_options *options)
>  	if (output_format & DIFF_FORMAT_NO_OUTPUT &&
>  	    options->flags.exit_with_status &&
>  	    options->flags.diff_from_contents) {
> +		/*
> +		 * run diff_flush_patch for the exit status. setting
> +		 * options->file to /dev/null should be safe, because we
> +		 * aren't supposed to produce any output anyway.
> +		 */
> +		diff_free_file(options);
> +		options->file = xfopen("/dev/null", "w");
> +		options->close_file = 1;
> +		options->color_moved = 0;
>  		for (i = 0; i < q->nr; i++) {
>  			struct diff_filepair *p = q->queue[i];
>  			if (check_pair_status(p))
>
> That would catch the bug here, as well as any others lurking. And it
> converts any missing dry_run from correctness problems (we definitely
> will not produce extra output) into optimization problems (we might emit
> data we do not need, but we can fix those separately). At least for the
> normal code paths. I think without those extra fixes the problems that
> b55e6d36eb tried to fix for "-I" would still be observable, but at least
> its fixes could not regress the other code paths.