From: Junio C Hamano <gitster@pobox.com>
Date: Fri, 24 Oct 2025 17:22:52 GMT
Subject: Re: [PATCH 3/4] diff: replace diff_options.dry_run flag with NULL file
Message-ID: <xmqqcy6cp637.fsf@gitster.g>
In-Reply-To: <20251024170853.GC2345184@coredump.intra.peff.net>

Jeff King <peff@peff.net> writes:

> We introduced a dry_run flag to diff_options in b55e6d36eb (diff: ensure
> consistent diff behavior with ignore options, 2025-08-08), with the idea
> that the lower-level diff code could skip output when it is set.
>
> As we saw with the bugs fixed by 3ed5d8bd73 (diff: stop output garbled
> message in dry run mode, 2025-10-20), it is easy to miss spots. In the
> end, we located all of them by checking where diff_options.file is used.
>
> That suggests another possible approach: we can replace the dry_run
> boolean with a NULL pointer for "file", as we know that using "file" in
> dry_run mode would always be an error. This turns any missed spots from
> producing extra output[1] into a segfault. Which is less forgiving, but
> that is the point: this is indicative of a programming error, and
> complaining loudly and immediately is good.

Makes sense.