Re: [PATCH 2/2] branch: clear target branch configuration before copying or renaming

> It does allude the _expected_ result, though ("[-C] uses the same underlying
> machinery as the --move (-m) option except the reflog and configuration is
> copied instead of being moved").
> 
>>
>> The design decisions in branch.c and config.c have brought us to this
>> unexpected result, which just need to be addressed. IMHO
> 
> It's helpful to reviewers and future readers to include relevant context in
> a commit message; a commit doesn't need to be responsible for a bug to help
> someone understand what you're trying to do and why. In this case, I needed
> to search through the commit history myself to gather that information (that
> is, how you decided clearing the destination first was the "correct"
> approach rather than, say, preserving the destination branch's config and
> not copying the source's), so I would consider the explanation in the
> current commit message incomplete. 
> 
> In general, it's often not enough to "just fix a bug" without elaborating on
> why something *is* a bug. This isn't an obvious thing like a 'BUG()' or
> segfault, so context like 52d59cc6452 is needed to convey the nuance of the
> issue.

>>>> +	test_when_finished git branch -D moved &&
>>>> +	git branch -t main-tracked main &&
>>>> +	git branch non-tracked &&
>>>> +	git branch -M main-tracked moved &&
>>>> +	git branch --unset-upstream moved &&
>>>> +	git branch -M non-tracked moved &&
>>>> +	test_must_fail git branch --unset-upstream moved
>>>
>>> If I'm reading this correctly, the test doesn't actually demonstrate that
>>> 'git branch -M' cleans up the tracking info, since 'moved' never has any
>>> tracking info immediately before 'git branch -M'. The test could also be
>>> more precise by verifying the upstream name matches. What about something
>>> like this?
>>>
>>> 	test_when_finished git branch -D moved &&
>>> 	git branch -t main-tracked main &&
>>> 	git branch non-tracked &&
>>>
>>> 	# `moved` doesn't exist, so it starts with no tracking info
>>> 	echo main >expect &&
>>> 	git branch -M main-tracked moved &&
>>> 	git rev-parse --abbrev-ref moved@{upstream} >actual &&
>>> 	test_cmp expect actual &&
>>>
>>> 	# At this point, `moved` is tracking `main`
>>> 	git branch -M non-tracked moved &&
>>> 	test_must_fail git rev-parse --abbrev-ref moved@{upstream}
>>
>> You are right, good eye.  Thanks.  That first '--unset-upstream'
>> eliminates the possible undesired inherited tracking info.  Removing it
>> is needed to make the test meaningful.  'rev-parse' is a good change,
>> but as the test is not testing that '-M' works as expected but doesn't
>> work in the unexpected way the message describes, I don't think we need
>> it here, imho.
> 
> But by always having the destination branch have no tracking info, this test
> doesn't verify that the unexpected behavior (that is, "mixing" the source
> and destination config) has been fixed. You still need a case where the
> destination config is non-empty and the source is empty (or some other
> non-empty value) to reproduce the issue.

> As for the 'rev-parse' vs. '--unset-upstream': making the test more precise
> here doesn't increase its scope *and* makes the overall test suite more
> effective at detecting regressions. And, a read-only check like 'rev-parse'
> is more readable for other developers (especially if they need to debug the
> test in the future), rather than needing to understand that

> '--unset-upstream' is doing two things: throwing an error depending on the
> presence of an upstream *and* removing the upstream from the target branch). 
> 
> In other words, it helps to separate your assertions from your setup steps.
> If you still need to '--unset-upstream' for the rest of the test, you can do
> the 'rev-parse' then '--unset-upstream' as two separate steps. 
> 
>> --- >8 ---
>>
>> Thank you!
>>
>>  t/t3200-branch.sh | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
>> index c3b3d11c28..ba959a82de 100755
>> --- a/t/t3200-branch.sh
>> +++ b/t/t3200-branch.sh
>> @@ -218,17 +218,16 @@ test_expect_success 'git branch -M should leave orphaned HEAD alone' '
>>  	)
>>  '
>>  
>> -test_expect_success 'git branch -M inherites clean tracking setup' '
>> +test_expect_success 'git branch -M inherits clean tracking setup' '
>>  	test_when_finished git branch -D moved &&
>>  	git branch -t main-tracked main &&
>>  	git branch non-tracked &&
>> -	git branch -M main-tracked moved &&
>>  	git branch --unset-upstream moved &&
>>  	git branch -M non-tracked moved &&
>>  	test_must_fail git branch --unset-upstream moved
> 
> This change makes the test less comprehensive (by removing the
> "tracked-overwrites-untracked" case) and does not solve the issue of 'moved'
> always having no tracking info before the 'git branch -M' (therefore not
> properly reproducing the error case fixed in this patch).

>>  '
>>  
>> -test_expect_success 'git branch -C inherites clean tracking setup' '
>> +test_expect_success 'git branch -C inherits clean tracking setup' '
>>  	test_when_finished git branch -D copiable copied &&
>>  	git branch -t copiable main &&
>>  	git branch -C copiable copied &&
>>
>