Re: [RFC/PATCH 1/2] commit: add parse_commit_repl() to replace commits at parsing time

From: Nguyen Thai Ngoc Duy <pclouds@gmail.com>
Date: Aug 18, 2010, 03:17 UTC
Message-ID: <AANLkTimu0r_3L7_YJgfMVb6saFOyOK-mHLiKyTG_6Q5O@mail.gmail.com>
In-Reply-To: <7vbp91aqfk.fsf@alter.siamese.dyndns.org>

On Wed, Aug 18, 2010 at 7:18 AM, Junio C Hamano <gitster@pobox.com> wrote:

Show 16 quoted lines

> Christian Couder <chriscool@tuxfamily.org> writes:
>
>> The function parse_commit() is not safe regarding replaced commits
>> because it uses the buffer of the replacement commit but the object
>> part of the commit struct stay the same. Especially the sha1 is not
>> changed so it doesn't match the content of the commit.
>
> This all sounds backwards to me, if I am reading the discussion correctly.
>
> If a replace record says commit 0123 is replaced by commit 4567 (iow, 0123
> was a mistake, and pretend that its content is what is recorded in 4567),
> and when we are honoring the replace records (iow, we are not fsck),
> shouldn't read_sha1("0123") give us a piece of memory that stores what is
> recorded in 4567, parse_object("0123") return a struct commit whose buffer
> points at a block of memory that has what is recorded in 4567 _while_ its
> object.sha1[] say "0123"?

1. parse_object() as it is now would return object.sha1[] = "4567".
2. lookup_commit(), then parse_commit() would return object.sha1[] = "0123".

> What problem are you trying to solve?

Inconsistency in replacing objects. I have no comments whether #1 or #2 is expected behavior. But at least it should stick to one behavior only.

-- 
Duy