Re: Can we clarify the purpose of `git diff -s`?

From: Junio C Hamano <gitster@pobox.com>
Date: May 12, 2023, 17:03 UTC
Message-ID: <xmqqo7mpqy6g.fsf@gitster.g>
In-Reply-To: <4f713a29-1a34-2f71-ee54-c01020be903a@univ-lyon1.fr>

Matthieu Moy <Matthieu.Moy@univ-lyon1.fr> writes:

Show 13 quoted lines

> https://public-inbox.org/git/51E3DC47.70107@googlemail.com/
>
> Essentially, Stefan Beller was using 'git show --format="%ad"' and
> expecting it to show only the author date, and for merge commits it
> also showed the patch (--cc). I suggested -s and noticed that the
> option wasn't easily discoverable, hence the patch series to better
> document it and add --no-patch as a synonym.
>
> Probably I did not get all the subtleties of the different kinds of
> outputs. I guess I considered the output of diff to be the one
> specified by --format plus the patch (not considering --raw, --stat &
> friends), hence "get only the output specified by --format" and
> "disable the patch" were synonym to me.

Thanks for double checking. It matches my recollection that we (you the author and other reviewers as well) added "--no-patch" back then to mean "no output from diff machinery, exactly the same as '-s' but use a name that is more discoverable".

Show 8 quoted lines

> Looking more closely, it's
> rather clear to me they are not, and that
>
>   git show --raw --patch --no-patch
>
> should be equivalent to
>
>   git show --raw

Yeah. If this were 10 years ago and we were designing from scratch, the "no output from diff machinery, more discoverable alias for '-s'" would have been "--silent" or "--squelch" and we would made any "--no-<format>" to defeat only "--<format>".

It is a different matter if we can safely change what "--no-patch" means _now_. Given that "--no-patch" was introduced for the explicit purpose of giving "-s" a name that is easier to remember, and given that in the 10 years since we did so, we may have acquired at least a few more end users of Git than we used to have, hopefully your change have helped them discover and learn to use "--no-patch" to defeat any "--<format>" they gave earlier as initial options in their script, which will be broken and need to be updated to use a much less discoverable "-s".

Thanks.