Fix dual rename into each other plus conflicting adds

This series adds some testcases based on the tensorflow repository issue reported by Glen Choo at [1], demonstrating bugs in both the ort and recursive strategies. It also provides a fix for the ort strategy.

Changes since v3:

* Remove use of for-initializer

Changes since v2:

* Added a couple preparatory cleanup patches
* Added a comment about why sub1/newfile is important to the new testcases
* A couple other minor code cleanups

Changes since v1:

* Fixed some wording issues in comments, and added a bit more details to one of the commit messages

[1]
https://lore.kernel.org/git/[email protected]/

Elijah Newren (5):
t6423: add tests of dual directory rename plus add/add conflict
merge-ort: small cleanups of check_for_directory_rename
merge-ort: make a separate function for freeing struct collisions
merge-ort: shuffle the computation and cleanup of potential collisions
merge-ort: fix issue with dual rename and add/add conflict

 merge-ort.c                         |  74 +++++++++++++-------
 t/t6423-merge-rename-directories.sh | 105 ++++++++++++++++++++++++++++
 2 files changed, 153 insertions(+), 26 deletions(-)

base-commit: e54793a95afeea1e10de1e5ad7eab914e7416250
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1268%2Fnewren%2Ffix-dual-rename-into-each-other-plus-conflicting-adds-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1268/newren/fix-dual-rename-into-each-other-plus-conflicting-adds-v4
Pull-Request: https://github.com/gitgitgadget/git/pull/1268

Range-diff vs v3:

 1:  a16a1c4d947 = 1:  a16a1c4d947 t6423: add tests of dual directory rename plus add/add conflict
 2:  297fef60b19 = 2:  297fef60b19 merge-ort: small cleanups of check_for_directory_rename
 3:  f5f87acbbd2 = 3:  f5f87acbbd2 merge-ort: make a separate function for freeing struct collisions
 4:  d3eac3d0bf6 ! 4:  9d813116112 merge-ort: shuffle the computation and cleanup of potential collisions
     @@ merge-ort.c: static int detect_and_process_renames(struct merge_options *opt,
       	ALLOC_GROW(combined.queue,
       		   renames->pairs[1].nr + renames->pairs[2].nr,
       		   combined.alloc);
     -+	for (int i = MERGE_SIDE1; i <= MERGE_SIDE2; i++) {
     ++	for (i = MERGE_SIDE1; i <= MERGE_SIDE2; i++) {
      +		int other_side = 3 - i;
      +		compute_collisions(&collisions[i],
      +				   &renames->dir_renames[other_side],
     @@ merge-ort.c: static int detect_and_process_renames(struct merge_options *opt,
      +				 collisions,
       				 &renames->dir_renames[1],
       				 &renames->dir_renames[2]);
     -+	for (int i = MERGE_SIDE1; i <= MERGE_SIDE2; i++)
     ++	for (i = MERGE_SIDE1; i <= MERGE_SIDE2; i++)
      +		free_collisions(&collisions[i]);
       	STABLE_QSORT(combined.queue, combined.nr, compare_pairs);
       	trace2_region_leave("merge", "directory renames", opt->repo);

5: 121761e26e2 = 5: 993ac405408 merge-ort: fix issue with dual rename and add/add conflict

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