Re: [PATCH v2 2/2] format-patch: warn if commit msg contains a patch delimiter

From: Junio C Hamano <gitster@pobox.com>
To: Phillip Wood <phillip.wood123@gmail.com>
Cc: Matheus Tavares <matheus.bernardino@usp.br>,
	git@vger.kernel.org, avarab@gmail.com, l.s.r@web.de
Subject: Re: [PATCH v2 2/2] format-patch: warn if commit msg contains a patch delimiter
Date: Wed, 07 Sep 2022 11:36:25 -0700	[thread overview]
Message-ID: <xmqqa67buj4m.fsf@gitster.g> (raw)
In-Reply-To: <4d750ff2-9df5-504f-9972-59b082000db0@gmail.com> (Phillip Wood's message of "Wed, 7 Sep 2022 19:09:05 +0100")

Phillip Wood <phillip.wood123@gmail.com> writes:

> Hi Matheus
>
> On 07/09/2022 15:44, Matheus Tavares wrote:
>> When applying a patch, `git am` looks for special delimiter strings
>> (such as "---") to know where the message ends and the actual diff
>> starts. If one of these strings appears in the commit message itself,
>> `am` might get confused and fail to apply the patch properly. This has
>> already caused inconveniences in the past [1][2]. To help avoid such
>> problem, let's make `git format-patch` warn on commit messages
>> containing one of the said strings.
>
> Thanks for working on this, having a warning for this is a useful
> addition. If the user embeds a diff in their commit message then they
> will receive three warnings
>
> warning: commit message has a patch delimiter: 'diff --git a/file b/file'
> warning: commit message has a patch delimiter: '--- file'
> warning: git am might fail to apply this patch. Consider indenting the
> offending lines.
>
> I guess it's helpful to show all the lines that are considered
> delimiters but it gets quite noisy.

True.  I wonder if automatically indenting these lines is an option ;-)

>> +
>> +	if (found_delimiter) {
>> +		warning(_("git am might fail to apply this patch. "
>> +			  "Consider indenting the offending lines."));
>
> The message says the patch might fail to apply, but isn't it
> guaranteed to fail?

Worse is it may apply a wrong thing (i.e. an illustration patch in
the proposed log message gets applied and committed with a truncated
log message).