From: Junio C Hamano <gitster@pobox.com>
To: Emily Shaffer <emilyshaffer@google.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>,
"Matheus Tavares Bernardino" <matheus.bernardino@usp.br>,
"Jonathan Nieder" <jrnieder@gmail.com>,
"Jacob Keller" <jacob.keller@gmail.com>,
"Atharva Raykar" <raykar.ath@gmail.com>,
"Derrick Stolee" <stolee@gmail.com>,
"Jonathan Tan" <jonathantanmy@google.com>
Subject: Re: [PATCH v6 0/5] teach submodules to know they're submodules
Date: Thu, 03 Feb 2022 14:39:17 -0800 [thread overview]
Message-ID: <xmqqczk3r2wa.fsf@gitster.g> (raw)
In-Reply-To: <20220203215914.683922-1-emilyshaffer@google.com> (Emily Shaffer's message of "Thu, 3 Feb 2022 13:59:10 -0800")
Emily Shaffer <emilyshaffer@google.com> writes:
> A couple things. Firstly, a semantics change *back* to the semantics of
> v3 - we map from gitdir to gitdir, *not* from common dir to common dir,
> so that theoretically a submodule with multiple worktrees in multiple
> superproject worktrees will be able to figure out which worktree of the
> superproject it's in. (Realistically, that's not really possible right
> now, but I'd like to change that soon.)
Sounds sensible.
> Secondly, a rewording of comments and commit messages to indicate that
> this isn't a cache of some expensive operation, but rather intended to
> be the source of truth for all submodules.
I'd expect that there is a way (e.g. "git fsck") that helps the
users notice when the actual filesystem layout contradicts with what
the gitdir-to-gitdir link says, and repair the repositories when
they go out of sync if possible.
It would be similar to "git worktree", where a link between the
".git" file that records "gitdir:" in a secondary worktree and the
repository's $GIT_DIR/worktrees/*/gitdir, and the "repair" command
can be used to bring them back in sync after moving the real
repository without telling the secondary worktree about the move.
> I did discuss Ævar's idea of relying on in-process filesystem digging to
> find the superproject's gitdir with the rest of the Google team, but in
> the end decided that there are some worries about filesystem digging in
> this way (namely, some ugly interactions with network drives that are
> actually already an issue for Googler Linux machines). Plus, the allure
> of being able to definitively know that we're a submodule is pretty
> strong.
The other side of the coin is that, even when a configuration
variable says that you are a submodule of the superproject at
location X, if such a submodule gets moved out of the superproject
(perhaps because the end-user wanted to concentrate on that
submodule project alone as an independent project) and the
superproject that used to be at location X got archived away,
trusting and relying on what the configuration variable says would
not help us access the now-gone superproject. And that would not
change no matter how strongly we declare that it is the source of
truth.
Unless we have a very good way to detect inconsistency and stop
spreading the damage (e.g. the setting thought our superproject sits
at directory X, but that location is now occupied by a different
repository that is not related), I am still skeptical about the
"setting is the sole truth" design.
next prev parent reply other threads:[~2022-02-03 22:39 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-17 0:56 [PATCH v6 0/5] teach submodules to know they're submodules Emily Shaffer
2021-11-17 0:56 ` [PATCH v6 1/5] t7400-submodule-basic: modernize inspect() helper Emily Shaffer
2021-11-17 0:56 ` [PATCH v6 2/5] introduce submodule.superprojectGitDir record Emily Shaffer
2021-11-17 23:43 ` Jonathan Tan
2021-11-17 0:56 ` [PATCH v6 3/5] submodule: record superproject gitdir during absorbgitdirs Emily Shaffer
2021-11-17 0:57 ` [PATCH v6 4/5] submodule: record superproject gitdir during 'update' Emily Shaffer
2021-11-17 0:57 ` [PATCH v6 5/5] submodule: use config to find superproject worktree Emily Shaffer
2021-11-17 11:43 ` [RFC PATCH 0/2] submodule: test what happens if submodule.superprojectGitDir isn't around Ævar Arnfjörð Bjarmason
2021-11-17 11:43 ` [RFC PATCH 1/2] submodule tests: fix potentially broken "config .. --unset" Ævar Arnfjörð Bjarmason
2021-11-17 11:43 ` [RFC PATCH 2/2] submodule: add test mode for checking absence of "superProjectGitDir" Ævar Arnfjörð Bjarmason
2021-11-23 20:08 ` [RFC PATCH 0/2] submodule: test what happens if submodule.superprojectGitDir isn't around Emily Shaffer
2021-11-24 1:38 ` Ævar Arnfjörð Bjarmason
2021-11-17 23:28 ` [PATCH v6 0/5] teach submodules to know they're submodules Jonathan Tan
2021-11-23 20:28 ` Emily Shaffer
2022-02-03 21:59 ` Emily Shaffer
2022-02-03 21:59 ` [PATCH v7 1/4] t7400-submodule-basic: modernize inspect() helper Emily Shaffer
2022-02-03 21:59 ` [PATCH v7 2/4] introduce submodule.superprojectGitDir record Emily Shaffer
2022-02-03 21:59 ` [PATCH v7 3/4] submodule: record superproject gitdir during absorbgitdirs Emily Shaffer
2022-02-03 21:59 ` [PATCH v7 4/4] submodule: record superproject gitdir during 'update' Emily Shaffer
2022-02-03 22:39 ` Junio C Hamano [this message]
2022-02-04 1:15 ` [PATCH v6 0/5] teach submodules to know they're submodules Ævar Arnfjörð Bjarmason
2022-02-04 16:20 ` Junio C Hamano
2022-02-07 19:56 ` Jonathan Nieder
2022-02-07 23:21 ` Junio C Hamano
2022-02-08 1:18 ` Jonathan Nieder
2022-02-08 18:24 ` Junio C Hamano
2022-02-10 22:12 ` Emily Shaffer
2022-02-10 22:53 ` Jonathan Nieder
2022-02-12 20:35 ` Ævar Arnfjörð Bjarmason
2022-02-13 6:25 ` Junio C Hamano
2022-03-01 0:26 ` [PATCH v8 0/3] " Emily Shaffer
2022-03-01 0:26 ` [PATCH v8 1/3] t7400-submodule-basic: modernize inspect() helper Emily Shaffer
2022-03-01 0:26 ` [PATCH v8 2/3] introduce submodule.hasSuperproject record Emily Shaffer
2022-03-01 7:00 ` Junio C Hamano
2022-03-08 20:04 ` Emily Shaffer
2022-03-08 22:13 ` Glen Choo
2022-03-08 22:29 ` Glen Choo
2022-03-01 0:26 ` [PATCH v8 3/3] rev-parse: short-circuit superproject worktree when config unset Emily Shaffer
2022-03-01 7:06 ` Junio C Hamano
2022-03-09 0:38 ` Emily Shaffer
2022-03-01 3:08 ` [PATCH v8 0/3] teach submodules to know they're submodules Junio C Hamano
2022-03-08 18:54 ` Emily Shaffer
2022-03-10 0:44 ` [PATCH v9 " Emily Shaffer
2022-03-10 0:44 ` [PATCH v9 1/3] t7400-submodule-basic: modernize inspect() helper Emily Shaffer
2022-03-10 0:44 ` [PATCH v9 2/3] introduce submodule.hasSuperproject record Emily Shaffer
2022-03-10 2:09 ` Junio C Hamano
2022-03-10 21:29 ` Glen Choo
2022-03-10 21:40 ` Glen Choo
2022-03-10 22:10 ` Junio C Hamano
2022-03-10 23:42 ` Glen Choo
2022-03-10 23:53 ` Glen Choo
2022-03-15 20:48 ` Emily Shaffer
2022-03-15 20:56 ` Emily Shaffer
2022-03-15 21:19 ` Glen Choo
2022-03-15 18:39 ` Emily Shaffer
2022-03-15 19:19 ` Junio C Hamano
2022-03-10 2:32 ` Junio C Hamano
2022-03-10 21:54 ` Glen Choo
2022-03-15 18:27 ` Emily Shaffer
2022-03-10 0:44 ` [PATCH v9 3/3] rev-parse: short-circuit superproject worktree when config unset Emily Shaffer
2022-03-10 1:47 ` Junio C Hamano
2022-03-10 4:39 ` Eric Sunshine
2022-03-11 9:09 ` [PATCH v9 0/3] teach submodules to know they're submodules Ævar Arnfjörð Bjarmason
2022-03-13 5:43 ` Junio C Hamano
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