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Re: [PATCH v7 17/31] merge-recursive: add a new hashmap for storing directory renames

From
Elijah Newren <newren@gmail.com>
Date
Feb 5, 2018, 14:56 UTC
Message-ID
<CABPp-BEJ5Ops0L2prJjLk9iNkMkVOOGtEOtUHevzXFCWgUAaeA@mail.gmail.com>
In-Reply-To
<911da66d-d6f3-2366-b2ae-4741ec9ff6d6@kdbg.org>
// Re-sending because of bounce
On Sun, Feb 4, 2018 at 12:54 AM, Johannes Sixt <j6t@kdbg.org> wrote:
Show 13 quoted lines
> Am 03.02.2018 um 22:34 schrieb Elijah Newren:
>>  If anyone can find an
>> example of a real world open source repository (linux, webkit, git,
>> etc.) with a merge where n is greater than about 10, I'll be
>> surprised.
>
> git rev-list --parents --merges master |
>  grep " .* .* .* .* .* .* .* .* .* .* "
>
> returns quite a few hits in the Linux repository. Most notable is
> fa623d1b0222adbe8f822e53c08003b9679a410c; spoiler: it has 30 parents.
>
> -- Hannes

Sorry, I didn't make it very clear what n represented. This is in the context of detecting directory renames, and in this discussion n represents the number of distinct directories that files were renamed into from a single original directory on a given side of the merge. So your example of number of parents of a commit isn't directly relevant to this case (also, even along your tangent, merge-recursive is only invoked when the number of parents is precisely two). However, I find your nugget rather interesting, even if unrelated. I had known of merges with more than 10 parents, but somehow was unaware that the limit of 16 parents had been lifted. And digging through the history, it was apparently removed quite a while ago. I love the commit message that lifted the limit too:

"There is no really good reason to have a merge with more than 16 parents, but we have a history of giving our users rope."

:-)
Previous: Johannes SixtNext: Junio C Hamano
Message 32 of 63 in “Add directory rename detection to git”
  1. 00/31 Add directory rename detection to gitElijah Newren, Jan 30, 2018
  2. Elijah NewrenJan 30, 2018
  3. 24/31 merge-recursive: when comparing files, don't include treesElijah Newren, Jan 30, 2018
  4. 28/31 merge-recursive: fix remaining directory rename + dirty overwrite casesElijah Newren, Jan 30, 2018
  5. Stefan BellerFeb 5, 2018
  6. Elijah NewrenFeb 5, 2018
  7. 05/31 directory rename detection: files/directories in the way of some renamesElijah Newren, Jan 30, 2018
  8. 06/31 directory rename detection: testcases checking which side did the renameElijah Newren, Jan 30, 2018
  9. 10/31 directory rename detection: tests for handling overwriting untracked filesElijah Newren, Jan 30, 2018
  10. 15/31 merge-recursive: make !o->detect_rename codepath more obviousElijah Newren, Jan 30, 2018
  11. Stefan BellerFeb 2, 2018
  12. 14/31 merge-recursive: fix leaks of allocated renames and diff_filepairsElijah Newren, Jan 30, 2018
  13. Stefan BellerFeb 2, 2018
  14. 23/31 merge-recursive: check for file level conflicts then get new nameElijah Newren, Jan 30, 2018
  15. 30/31 merge-recursive: avoid spurious rename/rename conflict from dir renamesElijah Newren, Jan 30, 2018
  16. 16/31 merge-recursive: split out code for determining diff_filepairsElijah Newren, Jan 30, 2018
  17. Stefan BellerFeb 3, 2018
  18. Elijah NewrenFeb 3, 2018
  19. 11/31 directory rename detection: tests for handling overwriting dirty filesElijah Newren, Jan 30, 2018
  20. 22/31 merge-recursive: add computation of collisions due to dir rename & mergingElijah Newren, Jan 30, 2018
  21. 31/31 merge-recursive: ensure we write updates for directory-renamed fileElijah Newren, Jan 30, 2018
  22. Stefan BellerFeb 5, 2018
  23. 20/31 merge-recursive: check for directory level conflictsElijah Newren, Jan 30, 2018
  24. Stefan BellerFeb 5, 2018
  25. Elijah NewrenFeb 5, 2018
  26. 25/31 merge-recursive: apply necessary modifications for directory renamesElijah Newren, Jan 30, 2018
  27. SZEDER GáborFeb 16, 2018
  28. 17/31 merge-recursive: add a new hashmap for storing directory renamesElijah Newren, Jan 30, 2018
  29. Stefan BellerFeb 3, 2018
  30. Elijah NewrenFeb 3, 2018
  31. Johannes SixtFeb 4, 2018
  32. Elijah NewrenFeb 5, 2018
  33. Junio C HamanoFeb 5, 2018
  34. Stefan BellerFeb 5, 2018
  35. Elijah NewrenFeb 5, 2018
  36. 21/31 merge-recursive: add a new hashmap for storing file collisionsElijah Newren, Jan 30, 2018
  37. Stefan BellerFeb 5, 2018
  38. 29/31 directory rename detection: new testcases showcasing a pair of bugsElijah Newren, Jan 30, 2018
  39. 27/31 merge-recursive: fix overwriting dirty files involved in renamesElijah Newren, Jan 30, 2018
  40. Stefan BellerFeb 5, 2018
  41. Elijah NewrenFeb 5, 2018
  42. 03/31 directory rename detection: testcases to avoid taking detection too farElijah Newren, Jan 30, 2018
  43. 01/31 directory rename detection: basic testcasesElijah Newren, Jan 30, 2018
  44. 04/31 directory rename detection: partially renamed directory testcase/discussionElijah Newren, Jan 30, 2018
  45. 19/31 merge-recursive: add get_directory_renames()Elijah Newren, Jan 30, 2018
  46. Stefan BellerFeb 3, 2018
  47. Elijah NewrenFeb 3, 2018
  48. Elijah NewrenFeb 4, 2018
  49. Eric SunshineFeb 4, 2018
  50. Eric SunshineFeb 4, 2018
  51. Stefan BellerFeb 5, 2018
  52. 18/31 merge-recursive: make a helper function for cleanup for handle_renamesElijah Newren, Jan 30, 2018
  53. Stefan BellerFeb 3, 2018
  54. 02/31 directory rename detection: directory splitting testcasesElijah Newren, Jan 30, 2018
  55. 13/31 merge-recursive: introduce new functions to handle rename logicElijah Newren, Jan 30, 2018
  56. Stefan BellerFeb 2, 2018
  57. 12/31 merge-recursive: move the get_renames() functionElijah Newren, Jan 30, 2018
  58. Stefan BellerFeb 2, 2018
  59. 09/31 directory rename detection: miscellaneous testcases to complete coverageElijah Newren, Jan 30, 2018
  60. 08/31 directory rename detection: testcases exploring possibly suboptimal mergesElijah Newren, Jan 30, 2018
  61. 26/31 merge-recursive: avoid clobbering untracked files with directory renamesElijah Newren, Jan 30, 2018
  62. 07/31 directory rename detection: more involved edge/corner testcasesElijah Newren, Jan 30, 2018
  63. Stefan BellerFeb 5, 2018

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