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Re: Git commit generation numbers

From
Phil Hord <hordp@cisco.com>
Date
Jul 21, 2011, 01:09 UTC
Message-ID
<4E277C2E.2020402@cisco.com>
In-Reply-To
<alpine.LFD.2.00.1107202041480.21187@xanadu.home>
On 07/20/2011 08:58 PM, Nicolas Pitre wrote:
Show 16 quoted lines
> On Wed, 20 Jul 2011, Phil Hord wrote:
>
>> On 07/20/2011 07:36 PM, Nicolas Pitre wrote:
>>> On Wed, 20 Jul 2011, david@lang.hm wrote:
>>>
>>>> If the generation number is part of the repository then it's going to
>>>> be the same for everyone.
>>> The actual generation number will be, and has to be, the same for
>>> everyone with the same repository content, regardless of the cache used.
>>> It is a well defined number with no room to interpretation.
>> Nonsense.
>>
>> Even if the generation number is well-defined and shared by all clients, the
>> only quasi-essential definition is "for each A in ancestors_of(B), gen(A)<
>> gen(B)".
> Sure.  But what do you gain by making holes in the sequence?

Depends on the algorithm. Probably speed. Possibly more efficient limited-cache building (jit-style discovery in reverse, as-needed, for example).

What do you gain by enforcing contiguousness? Why not require all gen numbers to be even? Or prime? ;)

Show 9 quoted lines
>> In practice, the actual generation number *will be the same* for everyone with
>> the same repository content, unless and until someone develops a different
>> calculation method.  But there is no reason to require that the number *has to
>> be* the same for everyone unless you expect (or require) everyone to share
>> their gen-caches.
> And with the above you clearly reinforced the argument _against_ storing
> the generation number in the commit object.  If you can imagine a
> different calculation method already, and if it is actually useful, then
> who knows if something even better could be done eventually.
Good.  Nice to see I'm being self-consistent, then.
Phil
Previous: Nicolas Pitre
Message 35 of 35 in “Re: Git commit generation numbers”
  1. George SpelvinJul 17, 2011
  2. Long, MartinJul 17, 2011
  3. Linus TorvaldsJul 17, 2011
  4. George SpelvinJul 17, 2011
  5. Linus TorvaldsJul 17, 2011
  6. George SpelvinJul 18, 2011
  7. Anthony Van de GejuchteJul 18, 2011
  8. George SpelvinJul 18, 2011
  9. Nicolas PitreJul 20, 2011
  10. George SpelvinJul 20, 2011
  11. david@lang.hmJul 20, 2011
  12. Nicolas PitreJul 20, 2011
  13. Phil HordJul 21, 2011
  14. david@lang.hmJul 21, 2011
  15. Shawn PearceJul 21, 2011
  16. Phil HordJul 21, 2011
  17. david@lang.hmJul 21, 2011
  18. George SpelvinJul 21, 2011
  19. Jakub NarebskiJul 21, 2011
  20. George SpelvinJul 21, 2011
  21. Shawn PearceJul 21, 2011
  22. Jakub NarebskiJul 22, 2011
  23. Nicolas PitreJul 22, 2011
  24. david@lang.hmJul 22, 2011
  25. Jakub NarebskiJul 22, 2011
  26. Linus TorvaldsJul 22, 2011
  27. Jeff KingJul 22, 2011
  28. Felipe ContrerasJul 28, 2011
  29. Ramkumar RamachandraSep 6, 2011
  30. david@lang.hmJul 22, 2011
  31. Nicolas PitreJul 22, 2011
  32. david@lang.hmJul 22, 2011
  33. Phil HordJul 21, 2011
  34. Nicolas PitreJul 21, 2011
  35. Phil HordJul 21, 2011

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