Re: [PATCH v2] receive-pack: purge temporary data if no command is ready to run

From: Junio C Hamano <gitster@pobox.com>
To: Chen BoJun <bojun.cbj@gmail.com>
Cc: git@vger.kernel.org, "Chen Bojun" <bojun.cbj@alibaba-inc.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Jiang Xin" <zhiyou.jx@alibaba-inc.com>,
	"Teng Long" <dyroneteng@gmail.com>
Subject: Re: [PATCH v2] receive-pack: purge temporary data if no command is ready to run
Date: Thu, 03 Feb 2022 17:17:44 -0800	[thread overview]
Message-ID: <xmqq5ypvpgzr.fsf@gitster.g> (raw)
In-Reply-To: <20220129063538.24038-1-bojun.cbj@gmail.com> (Chen BoJun's message of "Sat, 29 Jan 2022 14:35:38 +0800")

Chen BoJun <bojun.cbj@gmail.com> writes:

> +	/*
> +	 * If there is no command ready to run, should return directly to destroy
> +	 * temporary data in the quarantine area.
> +	 */
> +	for (cmd = commands; cmd && cmd->error_string; cmd = cmd->next)
> +		; /* nothing */
> +	if (!cmd)
> +		return;
> +
>  	/*
>  	 * Now we'll start writing out refs, which means the objects need
>  	 * to be in their final positions so that other processes can see them.

One thing I notice is that the first thing we do, after making the
new objects available to us, is to check if we are making any
conflicting update, e.g.

    git push origin master:master next:master

would try to update the same ref with different objects, and will be
rejected.

This check can _almost_ be doable without being able to access the
new objects, and as a follow-on work, it might not be a bad little
project to see how we can move the call to check_aliased_updates()
before this loop we are adding in this patch (#leftoverbits).

Thanks.