From: Junio C Hamano <gitster@pobox.com>
Date: Wed, 18 Jan 2017 20:57:12 GMT
Subject: Re: "git diff --ignore-space-change --stat" lists files with only whitespace differences as "changed"
Message-ID: <xmqqvatc3x3r.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <20170118111705.6bqzkklluikda3r5@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

> So I dunno. A sensible rule to me is "iff -p would show a diff header,
> then --stat should mention it".

True but tricky (you need a better definition of "a diff header").

In addition to a new and deleted file, does a file whose executable
bit was flipped need mention?  If so, then "diff --git" is the diff
header in the above.  Otherwise "@@ ... @@", iow, "iff -p would show
any hunk".

I think the patch implements the latter, which I think is sensible.

> +		/*
> +		 * Omit diffstats where nothing changed. Even if
> +		 * !same_contents, this might be the case due to ignoring
> +		 * whitespace changes, etc.
> +		 *
> +		 * But note that we special-case additions and deletions,
> +		 * as adding an empty file, for example, is still of interest.
> +		 */
> +		if (DIFF_FILE_VALID(one) && DIFF_FILE_VALID(two)) {
> +			struct diffstat_file *file =
> +				diffstat->files[diffstat->nr - 1];
> +			if (!file->added && !file->deleted) {
> +				free_diffstat_file(file);
> +				diffstat->nr--;
> +			}
> +		}
>  	}