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From: Eugeniu Rosca <erosca@de.adit-jv.com>
To: <gitster@pobox.com>, <peff@peff.net>, <avarab@gmail.com>,
	<git@vger.kernel.org>
Cc: Eugeniu Rosca <erosca@de.adit-jv.com>,
	Eugeniu Rosca <roscaeugeniu@gmail.com>
Subject: Unreliable 'git rebase --onto'
Date: Wed, 8 Jan 2020 22:43:49 +0100
Message-ID: <20200108214349.GA17624@lxhi-065.adit-jv.com> (raw)

Hello Git community,

Below is a simple reproduction scenario for what looks to be a bug (?)
in 'git rebase --onto' (v2.25.0-rc1-19-g042ed3e048af).

I would appreciate your confirmation of the misbehavior.
If the behavior is correct/expected, I would appreciate some feedback
how to avoid it in future, since it occurs with the default parameters.

1. git clone https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

2. ### Cherry pick an upstream commit, to contrast the results with
   'git rebase --onto':
   $ git checkout -b v4.18-cherry-pick v4.18
   $ git cherry-pick 463fa44eec2fef50
   Auto-merging drivers/input/touchscreen/atmel_mxt_ts.c
   warning: inexact rename detection was skipped due to too many files.
   warning: you may want to set your merge.renamelimit variable to at least 7216 and retry the command.
   [v4.18-cherry-pick bd142b45bf3a] Input: atmel_mxt_ts - disable IRQ across suspend
    Author: Evan Green <evgreen@chromium.org>
    Date: Wed Oct 2 14:00:21 2019 -0700
    1 file changed, 4 insertions(+)

3. ### In spite of the warning, the result matches the original commit:
   $ vimdiff <(git show 463fa44eec2fef50) <(git show v4.18-cherry-pick)

4. ### Now, backport the same commit via 'git rebase --onto'
   $ git rebase --onto v4.18 463fa44eec2fef50~ 463fa44eec2fef50
   First, rewinding head to replay your work on top of it...
   Applying: Input: atmel_mxt_ts - disable IRQ across suspend

5. ### The result is different:
   $ git branch v4.18-rebase-onto
   $ git diff v4.18-cherry-pick v4.18-rebase-onto

diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
index b45958e89cc5..2345b587662b 100644
--- a/drivers/input/touchscreen/atmel_mxt_ts.c
+++ b/drivers/input/touchscreen/atmel_mxt_ts.c
@@ -3139,8 +3139,6 @@ static int __maybe_unused mxt_suspend(struct device *dev)
 
 	mutex_unlock(&input_dev->mutex);
 
-	disable_irq(data->irq);
-
 	return 0;
 }
 
@@ -3162,6 +3160,8 @@ static int __maybe_unused mxt_resume(struct device *dev)
 
 	mutex_unlock(&input_dev->mutex);
 
+	disable_irq(data->irq);
+
 	return 0;
 }


In a nutshell, purely from user's perspective:
 - I get a warning from 'git cherry pick', with perfect results
 - I get no warning from 'git rebase --onto', with wrong results

Does git still behave expectedly? TIA!

-- 
Best Regards,
Eugeniu

             reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-08 21:43 Eugeniu Rosca [this message]
2020-01-08 22:35 ` SZEDER Gábor
2020-01-09  0:55   ` Elijah Newren
2020-01-09 15:03     ` SZEDER Gábor
2020-01-09 17:53       ` Elijah Newren
2020-01-21 19:18       ` [PATCH v1] rebase -i: stop checking out the tip of the branch to rebase Alban Gruin
2020-01-21 20:07         ` Elijah Newren
2020-01-22 20:24         ` Junio C Hamano
2020-01-22 20:47         ` Junio C Hamano
2020-01-24 14:45           ` Alban Gruin
2020-01-24 14:45         ` [PATCH v2] " Alban Gruin
2020-01-24 14:55           ` Alban Gruin
2020-01-24 18:12             ` Junio C Hamano
2020-01-24 15:05           ` [PATCH v3] " Alban Gruin
2020-01-24 18:30             ` Junio C Hamano
2020-02-05 14:31             ` Johannes Schindelin
2020-01-24 17:11           ` [PATCH v2] " Andrei Rybak
2020-01-09 11:13   ` Unreliable 'git rebase --onto' Eugeniu Rosca
     [not found] ` <CABPp-BHsyMOz+hi7EYoAnAWfzms7FRfwqCoarnu8H+vyDoN6SQ@mail.gmail.com>
2020-01-09 10:53   ` Eugeniu Rosca
2020-01-09 18:05     ` Elijah Newren
2020-01-10  0:06       ` Eugeniu Rosca
2020-01-10  2:35         ` Elijah Newren

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