Re: [PATCH v2 3/5] Makefile: don't needlessly "rm $@ $@+" before "mv $@+ $@"

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 29, 2021, 18:46 UTC
Message-ID: <xmqqft0dkdch.fsf@gitster.g>
In-Reply-To: <patch-3.6-96e2338ed8e-20210329T161723Z-avarab@gmail.com>

Ævar Arnfjörð Bjarmason  <avarab@gmail.com> writes:

Show 6 quoted lines

>     rm -f thing thing+
>     prepare contents for thing >thing+
>     mv thing+ thing
> ...
> But I think guarding against "mv" failing is a step too far in
> paranoia,...

If mv fails the $(MAKE) rule would fail, so it is OK. It may leave thing+ behind, but there is no reason to expect why you would be able to rm it the next time, so from that point of view, it is OK to drop the first "rm -f thing+", I would think. The only case I can thing of that would help is when you are sharing the working tree with your team member, the directories are writable to both of you, but somehow the other person creates thing+ with 0644 or 0755 mode bits. You cannot redirect into thing+ the other person left behind, but you can "rm -f thing+ && cmd >$thing+" (or "cmd -o $thing+") in such a situation, and that is probably where the pattern comes from ---i.e. simple hygiene.