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References: <cover.1585115341.git.liu.denton@gmail.com> <b51f97f6ae37e4b69b9651cbd60a480e5db3e72d.1585115341.git.liu.denton@gmail.com>
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In-Reply-To: <xmqqv9mtx7wv.fsf@gitster.c.googlers.com>
From:   Eric Sunshine <sunshine@sunshineco.com>
Date:   Wed, 25 Mar 2020 02:36:41 -0400
Message-ID: <CAPig+cSJVdFEZ_V_FBtdAhR7KqocqXCgkHm1pFMDjBX_NPE+Jw@mail.gmail.com>
Subject: Re: [PATCH 8/8] t5801: teach compare_refs() to accept !
To:     Junio C Hamano <gitster@pobox.com>
Cc:     Denton Liu <liu.denton@gmail.com>,
        Git Mailing List <git@vger.kernel.org>
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On Wed, Mar 25, 2020 at 2:31 AM Junio C Hamano <gitster@pobox.com> wrote:
> Denton Liu <liu.denton@gmail.com> writes:
> >  compare_refs() {
> > +     fail= &&
> > +     if test "x$1" = 'x!'
> > +     then
> > +             fail='!' &&
> > +             shift
> > +     fi &&
> >       git --git-dir="$1/.git" rev-parse --verify $2 >expect &&
> >       git --git-dir="$3/.git" rev-parse --verify $4 >actual &&
> > -     test_cmp expect actual
> > +     eval $fail test_cmp expect actual
> >  }
> > -     test_must_fail compare_refs local signed-tag server signed-tag
> > +     compare_refs ! local signed-tag server signed-tag
>
> While this is not wrong per-se, I do not know why we cannot just use
>
>         ! compare_refs local signed-tag server signed-tag
>
> i.e. "we expect these two repositories have different tags"?

As mentioned in the commit message, if one of the git-rev-parse
invocations fails unexpectedly, then compare_refs() would return early
with a failure code, but the "!" would then (undesirably) turn that
failure into a success. We don't want to lose a failure code from
git-rev-parse, so the simple use of "! compare_refs ..." is avoided.