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Re: [PATCH 00/17] Clean up how fetch_pack() handles the heads list

From
Junio C Hamano <gitster@pobox.com>
Date
Aug 24, 2012, 04:23 UTC
Message-ID
<7vd32g3ol6.fsf@alter.siamese.dyndns.org>
In-Reply-To
<20120823195648.GB15268@sigill.intra.peff.net>
Jeff King <peff@peff.net> writes:
Show 7 quoted lines
>> It may be (?) that it is a good time to think about a 'datedepth'
>> capability to bypass the current counted-depth shallow fetch that can
>> cause so much trouble. With a date limited depth the relevant tags
>> could also be fetched.
>
> I don't have anything against such an idea, but I think it is orthogonal
> to the issue being discussed here.
Correct.

The biggest problem with the "shallow" hack is that the deepening fetch counts from the tip of the refs at the time of deepening when deepening the history (i.e. "clone --depth", followed by number of "fetch", followed by "fetch --depth"). If you start from a shallow clone of depth 1, repeated fetch to keep up while the history grew by 100, you would still have a connected history down to the initial cauterization point, and "fetch --depth=200" would give you a history that is deeper than your original clone by 100 commits. But if you start from the same shallow clone of depth 1, did not do anything while the history grew by 100, and then decide to fetch again with "fetch --depth=20", it does not grow. It just makes 20-commit deep history from the updated tip, and leave the commit from your original clone dangling.

The problem with "depth" does not have anything to do with how it is specified at the UI level. The end-user input is used to find out at what set of commits the history is cauterized, and once they are computed, the "shallow" logic solely works on "is the history before these cauterization points, or after, in topological terms." (and it has to be that way to make sure we get reproducible results). Even if a new way to specify these cauterization points in terms of date is introduced, it does not change anything and does not solve the fundamental problem the code has when deepening.

Previous: Philip OakleyNext: Philip Oakley
Message 39 of 40 in “Clean up how fetch_pack() handles the heads list”
  1. 00/17 Clean up how fetch_pack() handles the heads listmhagger@alum.mit.edu, Aug 23, 2012
  2. 01/17 t5500: add tests of error output for missing refsmhagger@alum.mit.edu, Aug 23, 2012
  3. 02/17 Rename static function fetch_pack() to http_fetch_pack()mhagger@alum.mit.edu, Aug 23, 2012
  4. 03/17 Fix formatting.mhagger@alum.mit.edu, Aug 23, 2012
  5. 04/17 Name local variables more consistentlymhagger@alum.mit.edu, Aug 23, 2012
  6. Jeff KingAug 23, 2012
  7. Michael HaggertyAug 24, 2012
  8. Junio C HamanoAug 26, 2012
  9. Michael HaggertyAug 27, 2012
  10. Jeff KingAug 27, 2012
  11. Junio C HamanoAug 27, 2012
  12. Junio C HamanoAug 27, 2012
  13. 05/17 Do not check the same match_pos twicemhagger@alum.mit.edu, Aug 23, 2012
  14. Jeff KingAug 23, 2012
  15. 06/17 Let fetch_pack() inform caller about number of unique headsmhagger@alum.mit.edu, Aug 23, 2012
  16. Jeff KingAug 23, 2012
  17. Michael HaggertyAug 25, 2012
  18. 07/17 Pass nr_heads to do_pack_ref() by referencemhagger@alum.mit.edu, Aug 23, 2012
  19. 08/17 Pass nr_heads to everything_local() by referencemhagger@alum.mit.edu, Aug 23, 2012
  20. 09/17 Pass nr_heads to filter_refs() by referencemhagger@alum.mit.edu, Aug 23, 2012
  21. 10/17 Remove ineffective optimizationmhagger@alum.mit.edu, Aug 23, 2012
  22. 11/17 filter_refs(): do not leave gaps in return_refsmhagger@alum.mit.edu, Aug 23, 2012
  23. 12/17 filter_refs(): compress unmatched refs in heads arraymhagger@alum.mit.edu, Aug 23, 2012
  24. 13/17 cmd_fetch_pack: return early if finish_connect() returns an errormhagger@alum.mit.edu, Aug 23, 2012
  25. 14/17 Report missing refs even if no existing refs were receivedmhagger@alum.mit.edu, Aug 23, 2012
  26. 15/17 cmd_fetch_pack(): simplify computation of return valuemhagger@alum.mit.edu, Aug 23, 2012
  27. 16/17 fetch_pack(): free matching headsmhagger@alum.mit.edu, Aug 23, 2012
  28. Jeff KingAug 23, 2012
  29. 17/17 fetch_refs(): simplify logicmhagger@alum.mit.edu, Aug 23, 2012
  30. Jeff KingAug 23, 2012
  31. Michael HaggertyAug 25, 2012
  32. Jeff KingAug 23, 2012
  33. Philip OakleyAug 23, 2012
  34. Jeff KingAug 23, 2012
  35. Jeff KingAug 23, 2012
  36. Michael HaggertyAug 25, 2012
  37. Michael HaggertySep 2, 2012
  38. Philip OakleyAug 23, 2012
  39. Junio C HamanoAug 24, 2012
  40. Philip OakleyAug 24, 2012

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