From: Junio C Hamano <gitster@pobox.com>
To: Varun Naik <vcnaik94@gmail.com>
Cc: "René Scharfe" <l.s.r@web.de>,
git@vger.kernel.org, "Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>
Subject: Re: [RFC PATCH] unpack-trees.c: handle empty deleted ita files
Date: Thu, 15 Aug 2019 09:34:19 -0700 [thread overview]
Message-ID: <xmqqtvai4cc4.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <CAK_rgsGSfL2zQLP59O+PUCLGz0X8c4UQ3Zg=9M+nCww5C+X_gA@mail.gmail.com> (Varun Naik's message of "Thu, 15 Aug 2019 09:17:09 -0700")
Varun Naik <vcnaik94@gmail.com> writes:
> On Tue, Aug 13, 2019 at 1:33 PM Junio C Hamano <gitster@pobox.com> wrote:
>>
>> The original code considered that two entries with the same mode and
>> the same "contents" are the same. As nobody sane tracks an empty
>> file for an extended span of history, that meant that most of the
>> time, intent-to-add entries, which has the normal mode bits for the
>> blobs (with or without the executable bit) and object name for a
>> zero length blob, would have been judged "different".
>>
>
> I agree, this edge case is really arcane. The rabbit hole was deep :)
In retrospect, perhaps I shouldn't have used the empty-blob SHA-1
for I-T-A entries (instead, perhaps 0{40} or something impossible)
when I invented this feature at 39425819 ("git-add --intent-to-add
(-N)", 2008-08-21). It made the code to "diff" easier than having
to special case comparison between a real blob and an I-T-A entry,
but we are paying the price for that laziness with a discussion and
a patch like this one.
>> So perhaps
>>
>> + !ce_intent_to_add(a) && !ce_intent_to_add(b) &&
>>
>> i.e. "a cache entry is eligible to be same with something else only
>> when its I-T-A bit is unset".
>>
>
> I decided to follow René's suggestion in response to this. Patch coming soon.
Either is fine as the implementation of the same semantics; I
however am not sure if two I-T-A entries should compare "same" or
"not same", or if we are better off catching the caller that feeds
two I-T-A entries to same() with a BUG().
Thanks.
next prev parent reply other threads:[~2019-08-15 16:34 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-13 16:03 [RFC PATCH] unpack-trees.c: handle empty deleted ita files Varun Naik
2019-08-13 18:08 ` René Scharfe
2019-08-13 20:32 ` Junio C Hamano
2019-08-14 4:30 ` René Scharfe
2019-08-15 16:17 ` Varun Naik
2019-08-15 16:34 ` Junio C Hamano [this message]
2019-08-19 15:35 ` Varun Naik
2019-08-19 19:54 ` Junio C Hamano
2019-08-15 16:21 ` [PATCH v2] unpack-trees.c: distinguish ita files from empty files Varun Naik
2019-08-15 16:46 ` René Scharfe
2019-08-21 3:21 ` [PATCH v3] " Varun Naik
2020-02-14 17:14 ` [PATCH v4] " Varun Naik
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