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Re: Git commit generation numbers

From
Phil Hord <hordp@cisco.com>
Date
Jul 21, 2011, 00:08 UTC
Message-ID
<4E276DF8.8030301@cisco.com>
In-Reply-To
<alpine.LFD.2.00.1107201931510.21187@xanadu.home>
On 07/20/2011 07:36 PM, Nicolas Pitre wrote:
Show 7 quoted lines
> 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)".

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.

Surely there will be a competent and efficient gen-cache API. But most code can just ask if B --contains A or even just use rev-list and benefit from the increased speed of the answer. Because most code doesn't really care about the gen numbers themselves, but only the speed of determining ancestry.

Phil
Previous: Nicolas PitreNext: david@lang.hm
Message 13 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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