Re: Regression: git send-email Message-Id: numbering doesn't start at 1 any more

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

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Hello Junio,

On Tue, Nov 07, 2023 at 08:06:22AM +0900, Junio C Hamano wrote:
> Uwe Kleine-König <u.kleine-koenig@pengutronix.de> writes:
> 
> > Hello,
> >
> > Since commit 3ece9bf0f9e24909b090cf348d89e8920bd4f82f I experience that
> > the generated Message-Ids don't start at ....-1-... any more. I have:
> >
> > $ git send-email w/*
> > ...
> > Subject: [PATCH 0/5] watchdog: Drop platform_driver_probe() and convert to platform remove callback returning void (part II)
> > Date: Mon,  6 Nov 2023 16:10:04 +0100
> > Message-ID: <20231106151003.3844134-7-u.kleine-koenig@pengutronix.de>
> > ...
> >
> > So the cover letter is sent with Message-Id: ...-7-...
> 
> The above is consistent with the fact that a 5-patch series with a
> cover letter consists of 6 messages.  Dry-run uses message numbers
> 1-6 and forgets to reset the counter, so the next message becomes 7.
> As you identified, the fix in 3ece9bf0 (send-email: clear the
> $message_id after validation, 2023-05-17) for the fallout from an
> even earlier change to process each message twice still had left an
> observable side effect subject to the Hyrum's law, it seems.
> 
> > +my ($message_id_stamp, $message_id_serial);
> >  if ($validate) {
> >  	# FIFOs can only be read once, exclude them from validation.
> >  	my @real_files = ();
> > @@ -821,6 +822,7 @@ sub is_format_patch_arg {
> >  	}
> >  	delete $ENV{GIT_SENDEMAIL_FILE_COUNTER};
> >  	delete $ENV{GIT_SENDEMAIL_FILE_TOTAL};
> > +	$message_id_serial = 0;
> >  }
> 
> This fix looks quite logical to me, but even with this, the side
> effects of the earlier "read message twice" persists in end-user
> observable form, don't they?  IIRC, when sending out an N message
> series, we start from the timestamp as of N seconds ago and give
> each message the Date: header that increments by 1 second, which
> would mean the validator will see Date: that is different from what
> will actually be sent out, and more importantly, the messages sent
> out for real will have timestamps from the future, negating the
> point of starting from N seconds ago in the first place.

The series I used as an example here was finally sent out with
git-send-email patched with my suggested change.

The Message-Ids involved are:

	20231106154807.3866712-1-u.kleine-koenig@pengutronix.de
	20231106154807.3866712-2-u.kleine-koenig@pengutronix.de
	20231106154807.3866712-3-u.kleine-koenig@pengutronix.de
	20231106154807.3866712-4-u.kleine-koenig@pengutronix.de
	20231106154807.3866712-5-u.kleine-koenig@pengutronix.de
	20231106154807.3866712-6-u.kleine-koenig@pengutronix.de

So the Ids are are identical apart from the number this report is about.

> Your script may not have been paying attention to it and only noticed
> the difference in id_serial, but somebody else would complain the
> difference coming from calling gen_header more than once for each
> messages since a8022c5f (send-email: expose header information to
> git-send-email's sendemail-validate hook, 2023-04-19).
> 
> So, I dunno.  Michael, what do you think?  It appears to me that a
> more fundamental fix to the fallout from a8022c5f might be needed
> (e.g., we still let gen_header run while validating, but once
> validation is done, save the headers that validator saw and use them
> without calling gen_header again when we send the messages out, or
> something), if we truly want to be regression free.

That sounds sane.

> By the way, out of curiosity, earlier you said your script looks at
> the Message-IDs and counts the number of messages.  How does it do
> that?  Does it read the output of send-email and pass the messages
> to MTA for sending out for real?

The output of git send-email dumps the messages it sends out and then I
pick the message-id of the last mail by cut-n-paste and call my script
with that as a parameter. It then adds notes to the $commitcount topmost
commits such that I have something like this on the sent out commits:

	Notes:
	    Forwarded: id:20231106154807.3866712-2-u.kleine-koenig@pengutronix.de (v1)

This is very convenient to find the thread to ping if a patch doesn't
make it into the next release.

(By the way, one difficulty in my script is that depending on the series
having a cover letter or not I have to apply the id:....-1-... marker or
not. Would be great if git send-email started with ...-0-... for a
series with a cover letter. Detecting that reliably isn't trivial I
guess.)

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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