Re: Unreliable 'git rebase --onto'

> 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!