Re: Need to change old commit (and regenerate tree)

From: Antriksh Pany <antriksh.pany@gmail.com>
Date: May 21, 2010, 18:18 UTC
Message-ID: <AANLkTin77rXsU28ikOZx8mxpQANHjaEET--RiR6lGd3a@mail.gmail.com>
In-Reply-To: <AANLkTim0M-PJC655bhfcQ6mBYTPt9TK9Ys8qJBJd1UPS@mail.gmail.com>

Hi Jon

I guess the parent of both B~3 as well as C~6 is A2. So if, as you say, the time can be made identical, they should yield the same SHA1 IMHO.

On Fri, May 21, 2010 at 12:05 AM, Jon Seymour <jon.seymour@gmail.com> wrote:

Show 26 quoted lines

> On Fri, May 21, 2010 at 8:09 AM, Andreas Schwab <schwab@linux-m68k.org> wrote:
>> Antriksh Pany <antriksh.pany@gmail.com> writes:
>>
>>> Instead of (what I initially expected):
>>>
>>> A--------o--------o--------o--------o(old B)--------o--------o--------o(old C)
>>>
>>> A2--------o--------o--------o--------B--------o--------o--------C
>>>
>>>
>>> So what I am missing here? Aren't the new commits B~1, B~2, B~3
>>> identical to C~4, C~5, C~6 (respectively) in all ways so as to have
>>> gotten them the same SHA1 and hence appear as what I expected them to
>>> appear?
>>
>> No, they have a different commit time, which is also part of the hash.
>>
>
> Of course, even if the commit time was forged to be the same, the
> parent of B~3 is different to the parent of C~6 and since the parent
> is also contributes bits to the respective hashes, B~3 will
> necessarily (unlikely hash collisions excepted!) have a different hash
> to C~6
>
> jon.
>