From: Michael Montalbo <mmontalbo@gmail.com>
Date: Wed, 20 May 2026 20:21:33 GMT
Subject: Re: [BUG] "git diff --word-diff" gives a diff while they are only space changes
Message-ID: <CAC2QwmLXk=CXNo8+Ja0fL5pN1YYMTkh7XHAUwN1c9VxuFhyy4Q@mail.gmail.com>
In-Reply-To: <xmqqo6ic8564.fsf@gitster.g>

On Mon, May 18, 2026 at 8:11 PM Junio C Hamano <gitster@pobox.com> wrote:
>
> Chris Torek <chris.torek@gmail.com> writes:
>
> > Call it an "implementation note" (or, if you like, a "practical
> > consideration"?).
> > Something along these lines might work...
> >
> >   Implementation Note
> >
> >   The --word-diff option currently operates by taking the same
> >   line by line diff that you get without the option, then massaging
> >   the result into a word-by-word difference. This may cause an
> >   unnecessarily-larger diff than you would see with a more-clever
> >   implementation. If and when Git acquires a more-clever
> >   implementation, the output may change. Note that this is
> >   similar to the --diff-algorithm option, which may change the
> >   output.
> >
> >   Regardless of which algorithm is used, _any_ diff simply shows
> >   _a_ way to achieve some particular change. It's impossible for
> >   any algorithm to tell whether someone deleted two lines and
> >   then put one back exactly as it appeared earlier, saving the
> >   resulting text, vs deleting a single line, for instance. Only a
> >   keystroke-by-keystroke logger would be able to tell what the
> >   human operator actually typed into some editor. Git does
> >   not have that information, and having it is not desired.
> >
> > Chris
>
> I understand your frustration in the second paragraph ;-) but let's
> not go there.  The first paragraph is excellent.  It gives readers a
> clear enough explanation to understand what is happening and stop
> complaining where there is nothing to complain about (which is
> already hinted by the "Note that" at the end).
>

Thanks for the ideas, Chris. Here is my attempt at synthesizing Chris'
suggestions and Junio's feedback:

  The `--word-diff` option operates by taking the same line-by-line
  diff that is produced without the option and computing
  word-by-word changes within each hunk.  This may produce a
  larger diff than a dedicated word-diff tool would.  If Git
  acquires a different implementation in the future, the output
  may change.  Note that this is similar to the `--diff-algorithm`
  option, which may also change the output.

Does this work?