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From: Junio C Hamano <gitster@pobox.com>
To: Elijah Newren <newren@gmail.com>
Cc: Leif Middelschulte <leif.middelschulte@gmail.com>,
	Stefan Beller <sbeller@google.com>,
	Git Mailing List <git@vger.kernel.org>
Subject: Re: [PATCH 1/1] Inform about fast-forwarding of submodules during merge
Date: Mon, 21 May 2018 13:12:56 +0900
Message-ID: <xmqqzi0t1waf.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <CABPp-BGGe3r_QiC5264xkj0cp2Vu6WoLQZeDGEJi4eOpUW9z3g@mail.gmail.com>

Elijah Newren <newren@gmail.com> writes:

> Thanks for continuing to push on this.  This looks good so far (to
> me), but I was also hoping to see the analogy between these messages
> and "Auto-merging $FILE" for regular files mentioned.  Both Junio[1]
> and I[2] pointed out this similarity, and I think this
> similarity/analogy is useful additional motivation for making this
> change.

... meaning that it should be discussed and named as the primary
reason why this change is a good idea?

Re-reading what Leif wrote in the first paragraph, I tend to think
that "the more recent version may break us" Leif gives is not a
particularly convincing one.  After all, if we did not change the
commit bound at a submodule since we forked, while they changed it
to something else (either old or new), even though our changes may
have been fully tested with the version of the submodule we have
been testing with, it may break with the version the merged branch
has been using.  Such an update is cleanly and silently resolved at
the tree-level three-way merge, but the risk of breakage is no
different to the case this patch adds new notices to.

More importantly, the same "the changes we made may get broken by
changes in areas that are textually unrelated they made" will happen
without submodules.  Content-level three-way merges that resolves
cleanly at the textual level may need to get semantic adjustment.
Do we treat clean 3-way content merges as suspicious and give a
similar warning?  That smells like madness.

But as you said, we give "Auto-merging $FILE" notice to clean 3-way
merge at the content-level for normal files, and there is no good
reason why we should not do the same for submodules when one
fast-forwards to the other, which is an analogue to the
content-level 3-way merge where one branch's version is a superset
of the other ones.  And that is quite a convincing reason why a new
"Auto-merging $SUBMODULE" notice is a good idea.

> ...
> Also, by analogy to the "Auto-merging $FILE" comparison, the "to %s"
> on these two lines feels out of place.  Users can just look at the
> submodule to see what it was updated to.  In a sea of output from
> merging, this extra detail feels like noise for the standard use-case,
> unless I'm misunderstanding how submodules are special.

Now you meantion it, that part of the message does look more like a
debugging aid than a feature that helps actual end-users.  After
all, if our side did not change the commit recorded for the
submodule while their side changed, we do not report the result of
such a tree-level three-way merge that takes what commit they had at
their tip.

  reply index

Thread overview: 99+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-17  6:01 What's cooking in git.git (May 2018, #02; Thu, 17) Junio C Hamano
2018-05-17  6:39 ` jk/branch-l-0-deprecation (was Re: What's cooking in git.git (May 2018, #02; Thu, 17)) Kaartic Sivaraam
2018-05-17  9:48   ` Ævar Arnfjörð Bjarmason
2018-05-17 11:00     ` Kaartic Sivaraam
2018-05-17 12:02       ` Ævar Arnfjörð Bjarmason
2018-05-17 13:36     ` Jeff King
2018-05-24 15:10       ` Kaartic Sivaraam
2018-05-24 19:22         ` Jeff King
2018-05-24 19:31           ` [PATCH] branch: issue "-l" deprecation warning after pager starts Jeff King
2018-05-25  1:55             ` Junio C Hamano
2018-05-25  2:40               ` Jeff King
2018-05-25  8:56                 ` Junio C Hamano
2018-05-25  9:14                   ` Junio C Hamano
2018-05-25 17:10                     ` Jeff King
2018-05-26  2:37                       ` Junio C Hamano
2018-05-25 21:00                     ` [RFC PATCH 0/3] usage: prefix all lines in `vreportf()`, not just the first Martin Ågren
2018-05-25 21:00                       ` [RFC PATCH 1/3] usage: extract `prefix_suffix_lines()` from `advise()` Martin Ågren
2018-05-28  8:27                         ` Junio C Hamano
2018-05-28 18:40                         ` Duy Nguyen
2018-05-29 21:33                           ` Jeff King
2018-05-29 21:39                         ` Jeff King
2018-05-30  1:42                           ` Junio C Hamano
2018-05-30  6:00                             ` Junio C Hamano
2018-05-30 10:26                               ` Martin Ågren
2018-05-31  6:07                                 ` Jeff King
2018-05-25 21:00                       ` [RFC PATCH 2/3] usage: prefix all lines in `vreportf()`, not just the first Martin Ågren
2018-05-28  9:25                         ` Junio C Hamano
2018-05-28 18:45                           ` Duy Nguyen
2018-05-28 21:45                             ` Junio C Hamano
2018-05-29  4:49                               ` Martin Ågren
2018-05-29  5:50                                 ` Junio C Hamano
2018-05-29 10:30                                   ` Martin Ågren
2018-05-29 12:08                                     ` Junio C Hamano
2018-05-29 15:50                                 ` Duy Nguyen
2018-05-30 10:19                                   ` Martin Ågren
2018-05-29 21:32                           ` Jeff King
2018-05-30 10:20                             ` Martin Ågren
2018-05-25 21:00                       ` [RFC PATCH 3/3] usage: translate the "error: "-prefix and others Martin Ågren
2018-05-26  2:32                   ` [PATCH] branch: issue "-l" deprecation warning after pager starts Junio C Hamano
2018-05-26  2:33                     ` Junio C Hamano
2018-05-29 21:20                     ` Jeff King
2018-05-29 21:21                       ` Jeff King
2018-05-30  2:48                         ` Junio C Hamano
2018-05-31  5:44                           ` Jeff King
2018-05-26 19:39                 ` Kaartic Sivaraam
2018-06-02  4:46                 ` Duy Nguyen
2018-06-02  8:10                   ` Jeff King
2018-05-26 18:45             ` Kaartic Sivaraam
2018-05-29 21:15               ` Jeff King
2018-05-30  2:52                 ` Junio C Hamano
2018-05-31  5:51                   ` Jeff King
2018-06-01  1:35                     ` Junio C Hamano
2018-05-31  5:52                   ` Kaartic.Sivaraam
2018-05-17 13:22 ` What's cooking in git.git (May 2018, #02; Thu, 17) Derrick Stolee
2018-05-17 18:20 ` Stefan Beller
2018-05-17 18:29   ` [PATCH 0/2] Reroll 2 last commits of sb/object-store-replace Stefan Beller
2018-05-17 18:29     ` [PATCH 1/2] object.c: free replace map in raw_object_store_clear Stefan Beller
2018-05-17 18:29     ` [PATCH 2/2] replace-object.c: remove the_repository from prepare_replace_object Stefan Beller
2018-05-17 18:40   ` [PATCH] merge-recursive: give notice when submodule commit gets fast-forwarded Stefan Beller
2018-05-18 19:43     ` [PATCH v2 0/1] rebased: inform about auto submodule ff Leif Middelschulte
2018-05-18 19:48     ` [PATCH v3 " Leif Middelschulte
2018-05-18 19:48       ` [PATCH 1/1] Inform about fast-forwarding of submodules during merge Leif Middelschulte
2018-05-18 21:25         ` Elijah Newren
2018-05-21  4:12           ` Junio C Hamano [this message]
2018-05-17 19:46   ` [PATCH 0/8] Reroll of sb/diff-color-move-more Stefan Beller
2018-05-17 19:46     ` [PATCH 1/8] xdiff/xdiff.h: remove unused flags Stefan Beller
2018-05-17 19:46     ` [PATCH 2/8] xdiff/xdiffi.c: remove unneeded function declarations Stefan Beller
2018-05-17 19:46     ` [PATCH 3/8] diff.c: do not pass diff options as keydata to hashmap Stefan Beller
2018-05-17 19:46     ` [PATCH 4/8] diff.c: adjust hash function signature to match hashmap expectation Stefan Beller
2018-05-17 19:46     ` [PATCH 5/8] diff.c: add a blocks mode for moved code detection Stefan Beller
2018-05-17 19:46     ` [PATCH 6/8] diff.c: decouple white space treatment from move detection algorithm Stefan Beller
2018-05-18  4:00       ` Simon Ruderich
2018-05-18 19:25         ` Stefan Beller
2018-05-17 19:46     ` [PATCH 7/8] diff.c: add --color-moved-ignore-space-delta option Stefan Beller
2018-05-17 19:46     ` [PATCH 8/8] diff: color-moved white space handling options imply color-moved Stefan Beller
2018-05-17 22:53     ` [PATCH 0/8] Reroll of sb/diff-color-move-more Jonathan Tan
2018-06-07 23:54     ` Jacob Keller
2018-05-17 22:36   ` What's cooking in git.git (May 2018, #02; Thu, 17) Junio C Hamano
2018-05-17 22:39     ` Stefan Beller
2018-05-17 22:56     ` Junio C Hamano
2018-05-17 22:58       ` Stefan Beller
2018-05-21  1:57 ` brian m. carlson
2018-05-21 17:36   ` Stefan Beller
2018-05-25 12:28 ` sb/submodule-move-nested breaks t7411 under GIT_FSMONITOR_TEST Ævar Arnfjörð Bjarmason
2018-05-25 17:27   ` Stefan Beller
2018-05-25 19:49   ` Stefan Beller
2018-09-06 12:31     ` Ævar Arnfjörð Bjarmason
2018-09-06 16:57       ` Stefan Beller
2018-09-06 19:03         ` Ben Peart
2018-09-06 20:14           ` Stefan Beller
2018-09-06 20:34             ` [PATCH] git-mv: allow submodules and fsmonitor to work together Stefan Beller
2018-09-10 15:58               ` Ben Peart
2018-09-10 16:29                 ` [PATCH v1] " Ben Peart
2018-09-10 17:07                   ` Stefan Beller
2018-09-10 19:38                     ` Ben Peart
  -- strict thread matches above, loose matches on Subject: below --
2018-05-11  1:00 [PATCH 0/2] Submodule merging: i18n, verbosity Stefan Beller
2018-05-14 20:57 ` [PATCH 0/1] rebased: inform about auto submodule ff during merge Leif Middelschulte
2018-05-14 20:57   ` [PATCH 1/1] Inform about fast-forwarding of submodules " Leif Middelschulte
2018-05-15  0:41     ` Stefan Beller
2018-05-15  1:17     ` Elijah Newren
2018-05-15  7:34       ` Junio C Hamano

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