Re: Strange behaviour of git diff branch1 ... branch2

From: Junio C Hamano <gitster@pobox.com>
Date: Nov 12, 2012, 17:46 UTC
Message-ID: <7vbof2iuic.fsf@alter.siamese.dyndns.org>
In-Reply-To: <CACsJy8BkKRxp9AQW0M0vDSL8Mb16VGSrZ1OnQpwCrERWKVLSyA@mail.gmail.com>

Nguyen Thai Ngoc Duy <pclouds@gmail.com> writes:

Show 15 quoted lines

> On Sat, Oct 27, 2012 at 7:33 PM, Junio C Hamano <gitster@pobox.com> wrote:
>>
>> Nguyen Thai Ngoc Duy <pclouds@gmail.com> wrote:
>>>
>>>Notice the --cc in the first line, which is combined diff. Usually
>>>combined-diff is between two points and one parent. Though somehow git
>>>passes 4 parents down combined-diff.c:show_combined_header, as you can
>>>see in the "index" line. I think we should fix rev parsing code as it
>>>does not make sense to pass 4 identical parents this way.
>>
>> The two heads home from HEAD...HEAD the user has on the command line.
>>
>> The user is getting exactly what she asked; there is nothing to fix.
>
> Is there any use case where HEAD...HEAD (or "..." alone) is actually useful?

That is an invalid question, implying a proposal that will introduce more confusion to the users while hurting the code.

There is no use case where "cat A >>A" is actually useful, either, but it does not mean "cat A >>A" should be special cased to do something different from what it happens to do in line with the case where "cat A >>B" does. I think "diff ..." or "diff HEAD...HEAD" are the same as that example.