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From: Emily Shaffer <emilyshaffer@google.com>
To: Derrick Stolee <stolee@gmail.com>
Cc: git@vger.kernel.org, "Albert Cui" <albertcui@google.com>,
	"Phillip Wood" <phillip.wood123@gmail.com>,
	"Johannes Schindelin" <Johannes.Schindelin@gmx.de>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Junio C Hamano" <gitster@pobox.com>,
	"Matheus Tavares Bernardino" <matheus.bernardino@usp.br>,
	"Jonathan Nieder" <jrnieder@gmail.com>,
	"Jacob Keller" <jacob.keller@gmail.com>,
	"Atharva Raykar" <raykar.ath@gmail.com>,
	"Jonathan Tan" <jonathantanmy@google.com>
Subject: Re: [PATCH v3 0/4] cache parent project's gitdir in submodules
Date: Thu, 14 Oct 2021 11:52:42 -0700	[thread overview]
Message-ID: <YWh8ej9rWnxCBCKJ@google.com> (raw)
In-Reply-To: <461f5fa8-42a4-b9a0-b223-7f97b764efd0@gmail.com>

On Thu, Oct 14, 2021 at 01:12:11PM -0400, Derrick Stolee wrote:
> 
> On 10/13/2021 2:51 PM, Emily Shaffer wrote:
> > On Thu, Aug 19, 2021 at 09:09:46PM -0400, Derrick Stolee wrote:
> >> but I do have some concerns that
> >> we have not covered all the cases that could lead to the relative path
> >> needing an update, such as a 'git checkout' across commits in the super-
> >> project which moves a submodule.
> >>
> >> Leading more to my confusion is that I thought 'git submodule update'
> >> was the way to move a submodule, but that does not appear to be the case.
> >> I used 'git mv' to move a submodule and that correctly updated the
> >> .gitmodules file, but did not run any 'git submodule' subcommands (based
> >> on GIT_TRACE2_PERF=1).
> > 
> > During a live review a few weeks ago it was pointed out, I forget by
> > who, that this whole series would make a lot more sense if it was
> > treated as the path from the submodule's gitdir to the superproject's
> > gitdir. I think this would also fix your 'git mv' example here, as the
> > submodule gitdir would not change.
> 
> I think that's a great way to deliver similar functionality without
> the issues I was thinking about.
> 
> >> You mention in an earlier cover letter that this config does not need to
> >> exist, but it seems to me that if it exists it needs to be correct for us
> >> to depend on it for future features. I'm not convinced that we can rely
> >> on it as-written, but you might be able to convince me by pointing out
> >> why these submodule movements are safe.
> > 
> > Yeah, that is a good point, and I wonder how to be defensive about
> > this... Maybe it makes sense to BUG() if we don't find the
> > superproject's gitdir from this config? Maybe it makes sense to warn
> > (asking users to 'git submodule update') and erase the incorrect config
> > line?
> 
> I think we can complain with something like a die() if the config points
> to data that doesn't make sense (not a .git directory), but a BUG() is
> too heavy-handed because it can just be a user modifying their config
> file incorrectly.

Ok. Having re-thought since the other day, I think I will skip the
wrapper for this reroll and instead propose it in a series that actually
uses this pointer (so, the shared submodule-and-superproject config), if
it looks like we'd want one. I expect doing that work in the context of
a caller will make the correct behavior a little more clear - in the
context of this series I'm not totally sure what we'd want to do.

> 
> I'm happy to shut down a process because a user messed with config
> incorrectly. Since your proposed change allows operations like 'git mv'
> to move submodules without needing to change this config, I'm much
> happier with the design. It becomes impossible for the config to get
> out of sync unless the user does something outside of a Git command.

Thanks for pulling the context back up here. I appreciate it. Like I
mentioned in reply to your comment on v4, look for a reroll in the next
30 minutes or so (assuming the CI passes ok).

 - Emily

  reply	other threads:[~2021-10-14 18:52 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-11 22:54 [RFC PATCH 0/4] cache parent project's gitdir in submodules Emily Shaffer
2021-06-11 22:54 ` [RFC PATCH 1/4] t7400-submodule-basic: modernize inspect() helper Emily Shaffer
2021-06-14  4:52   ` Junio C Hamano
2021-06-11 22:54 ` [RFC PATCH 2/4] introduce submodule.superprojectGitDir cache Emily Shaffer
2021-06-14  5:09   ` Junio C Hamano
2021-06-15 22:00     ` Emily Shaffer
2021-06-11 22:54 ` [RFC PATCH 3/4] submodule: cache superproject gitdir during absorbgitdirs Emily Shaffer
2021-06-14  6:18   ` Junio C Hamano
2021-06-11 22:54 ` [RFC PATCH 4/4] submodule: cache superproject gitdir during 'update' Emily Shaffer
2021-06-14  6:22   ` Junio C Hamano
2021-06-15 21:27     ` Emily Shaffer
2021-06-12 20:12 ` [RFC PATCH 0/4] cache parent project's gitdir in submodules Jacob Keller
2021-06-14  7:26 ` Junio C Hamano
2021-06-15 21:18   ` Emily Shaffer
2021-06-16  0:45 ` [PATCH v2 " Emily Shaffer
2021-06-16  0:45   ` [PATCH v2 1/4] t7400-submodule-basic: modernize inspect() helper Emily Shaffer
2021-07-27 17:12     ` Jonathan Tan
2021-08-19 17:46       ` Emily Shaffer
2021-06-16  0:45   ` [PATCH v2 2/4] introduce submodule.superprojectGitDir cache Emily Shaffer
2021-06-16  4:40     ` Junio C Hamano
2021-06-16  4:43       ` Junio C Hamano
2021-06-18  0:03         ` Emily Shaffer
2021-06-18  0:00       ` Emily Shaffer
2021-07-27 17:46     ` Jonathan Tan
2021-08-19 17:53       ` Emily Shaffer
2021-10-14 19:25     ` Ævar Arnfjörð Bjarmason
2021-06-16  0:45   ` [PATCH v2 3/4] submodule: cache superproject gitdir during absorbgitdirs Emily Shaffer
2021-06-16  0:45   ` [PATCH v2 4/4] submodule: cache superproject gitdir during 'update' Emily Shaffer
2021-07-27 17:51     ` Jonathan Tan
2021-08-19 18:02       ` Emily Shaffer
2021-08-19 20:09   ` [PATCH v3 0/4] cache parent project's gitdir in submodules Emily Shaffer
2021-08-19 20:09     ` [PATCH v3 1/4] t7400-submodule-basic: modernize inspect() helper Emily Shaffer
2021-08-19 20:09     ` [PATCH v3 2/4] introduce submodule.superprojectGitDir record Emily Shaffer
2021-08-20  0:38       ` Derrick Stolee
2021-10-13 19:36         ` Emily Shaffer
2021-09-04 17:20       ` Matheus Tavares
2021-10-13 19:39         ` Emily Shaffer
2021-08-19 20:09     ` [PATCH v3 3/4] submodule: record superproject gitdir during absorbgitdirs Emily Shaffer
2021-08-20  0:50       ` Derrick Stolee
2021-10-13 19:42         ` Emily Shaffer
2021-09-04 17:27       ` Matheus Tavares
2021-10-14 18:40         ` Emily Shaffer
2021-08-19 20:09     ` [PATCH v3 4/4] submodule: record superproject gitdir during 'update' Emily Shaffer
2021-08-20  0:59       ` Derrick Stolee
2021-10-14 18:45         ` Emily Shaffer
2021-08-19 21:56     ` [PATCH v3 0/4] cache parent project's gitdir in submodules Junio C Hamano
2021-08-20  1:09     ` Derrick Stolee
2021-10-13 18:51       ` Emily Shaffer
2021-10-14 17:12         ` Derrick Stolee
2021-10-14 18:52           ` Emily Shaffer [this message]
2021-09-04 17:50     ` Matheus Tavares Bernardino

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