Re: [PATCH] Re-re-re-fix common tail optimization

From: Wincent Colaiuta <win@wincent.com>
Date: Dec 17, 2007, 10:59 UTC
Message-ID: <36E62F9B-26FF-4DC0-99B8-D6DC2B960E67@wincent.com>
In-Reply-To: <Pine.LNX.4.64.0712171038130.9446@racer.site>

El 17/12/2007, a las 11:39, Johannes Schindelin escribió:

Show 29 quoted lines

> Hi,
>
> On Mon, 17 Dec 2007, Wincent Colaiuta wrote:
>
>> El 16/12/2007, a las 23:29, Jeff King escribi?:
>>
>>> On Sun, Dec 16, 2007 at 02:23:27PM -0800, Junio C Hamano wrote:
>>>
>>>>> Aren't we using "git diff" for the second diff there nowadays?
>>>>
>>>> Some people seem to think that is a good idea, but I generally do
>>>> not like using "git diff" between expect and actual (both  
>>>> untracked)
>>>> inside tests.  The last "diff" is about validating what git does  
>>>> and
>>>> using "git diff" there would make the test meaningless when "git
>>>> diff" itself is broken.
>>>
>>> I think that is a valid concern. But ISTR that were some issues with
>>> using GNU diff. Commit 5bd74506 mentions getting rid of the  
>>> dependency
>>> in all existing tests, but gives no reason.
>>
>> I'd say it's safe and sensible to use "git diff" in all tests  
>> *except*
>> for tests of "git diff" itself.
>
> To the contrary.  It has to test "git diff", so it must use "git  
> diff".

Obviously, you can only test "git diff" by actually running it.

Show 7 quoted lines

> As for the reference output: we include the expected diffs as texts,  
> and
> therefore do not really have to rely on having GNU diff installed.
>
> Besides, we cannot even test the goodies like "rename from" by  
> comparing
> to GNU diff's output.

Sorry, I didn't make myself clear. That's not what I was proposing at all. I was talking about this kind of example:

> +	git diff -U0 | sed -e "/^index/d" -e "s/$z2047/Z/g" >actual &&
> +	diff -u expect actual

First line uses "git diff", if the second line uses "git diff" as well and "git diff" happens to be broken then you're using a broken tool to test a broken tool, as Junio already pointed out. I presumed that if you had read the whole thread then that would be obvious (look at the quoted section from Junio above).

In the example you're not interested in the details of the output format, only in the exit status, so it is appropriate to use diff instead of "git diff".

Wincent