Re: [BUG] "git diff --word-diff" gives a diff while they are only space changes

From: Vincent Lefevre <vincent@vinc17.net>
Date: May 14, 2026, 09:55 UTC
Message-ID: <20260514095522.GA159111@qaa.vinc17.org>
In-Reply-To: <xmqq8q9migqk.fsf@gitster.g>

On 2026-05-14 16:37:39 +0900, Junio C Hamano wrote:

Show 14 quoted lines

> Michael Montalbo <mmontalbo@gmail.com> writes:
> 
> > @@ -457,6 +457,11 @@ endif::git-diff[]
> >  +
> >  Note that despite the name of the first mode, color is used to
> >  highlight the changed parts in all modes if enabled.
> > ++
> > +Word diff works by finding word-level changes within each hunk of
> > +the line-level diff.  The line-level alignment determines which
> > +changed lines are compared to each other, which can affect the
> > +word-level output.
> 
> The added text may not say anything wrong, but I am not sure how it
> helps the end user to know the way machinery works internally.

Perhaps only the first sentence should be kept and that the following should be added: "Because of that, using the --ignore-space-change option is recommended."

Note: Earlier in the discussion, Johannes Sixt suggested -w
(--ignore-all-space), but this is wrong, as

  git diff --word-diff -w <(printf foo) <(printf "f o o")

gives no differences while one has 1 word "foo" vs 3 words "f o o".

However, --ignore-space-change is actually not even sufficient since

  git diff --ignore-space-change <(printf "foo bar") <(printf "foo\nbar")

finds differences though there are only space changes (thus this may affect hunks in case --word-diff would be used too). However, I suppose that the cases where --word-diff --ignore-space-change would not give a "real word diff" would be quite rare in practice.

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Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
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