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

[Jon Seymour <jon.seymour@gmail.com>]

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.