Re: "git diff --ignore-space-change --stat" lists files with only whitespace differences as "changed"

From: Junio C Hamano <gitster@pobox.com>
Date: Jan 18, 2017, 22:15 UTC
Message-ID: <xmqqtw8w2ewj.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <20170118210821.xugr6jnvzgoxpynb@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

Show 18 quoted lines

> On Wed, Jan 18, 2017 at 12:57:12PM -0800, Junio C Hamano wrote:
>
>> 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.
>
> I would think the former is more sensible (and is what my patch is
> working towards).

Doh (yes, "diff --git" was what I meant). As a mode-flipping patch does not have hunk but does show the header, it wants to be included in "git diff --stat" output, I would think, independent of -b issue. In fact

	chmod +x README.md
	git diff --stat

does show a 0-line diffstat.

Show 25 quoted lines

> Doing:
>
>   >empty
>   git add empty
>   git diff --cached
>
> shows a "diff --git" header, but no hunk. I think it should show a
> diffstat (and does with my patch).
>
> I was thinking the rule should be something like:
>
>   if (p->status == DIFF_STATUS_MODIFIED &&
>       !file->added && !file->deleted))
>
> and otherwise include the entry, since it would be an add, delete,
> rename, etc, which carries useful information.
>
> Though a pure rename would not hit this code path at all, I would think
> (it would not trigger "!same_contents"). And a rename where there was a
> whitespace only change probably _should_ be omitted from "-b".
>
> Ditto for a pure mode change, I think. We do not run the contents
> through diff at all, so it does not hit this code path.
>
> -Peff