In order to help Ævar test his tree-walk changes against merge-ort[1], this
series completes the merge-ort implementation and cleans up testsuite
failures...EXCEPT for some t6423 failures. It also leaves out a lot of
performance work, which incidentally will fix the t6423 failures and is
being reviewed independently[2].

This 11-patch series could be submitted as 7 independent series, 1-4 patches
in length each, but it's probably easier for Ævar if we can merge just one
more thing and it's only 11 total patches. This series sub-divides as
follows:

 * Patch 1: Fix bug in already-merged portion of merge-ort affecting
   rename/rename conflicts on platforms where qsort isn't stable. (Could be
   considered for merging before 2.31 since it is a new bug in the 2.31
   cycle that I just learned of last night, but not sure it matters since
   merge-ort wasn't complete anyway and we're not even mentioning merge-ort
   in the release notes.)
 * Patches 2-5: Add support for renormalization
 * Patch 6: Add support for subtree shifting
 * Patch 7-8: Add test and support for conflicts affecting sparse-checkout
   entries
 * Patch 9: Update submodule related merge tests to note the ones that
   merge-ort fixes relative to merge-recursive
 * Patch 10: New feature -- allow "git diff AUTO_MERGE" during conflict
   resolution to let user review changes they made since
   merge/rebase/cherry-pick/revert stopped and informed them of conflicts
 * Patch 11: Add comments noting various bugs in merge-recursive

The last two patches aren't needed by Ævar, so they could be left out and
submitted later. I just figured that it was only two more patches and they
were part of "completing the merge-ort implementation" in my view.

[1] https://lore.kernel.org/git/877dmmkhnt.fsf@evledraar.gmail.com/ [2] See
https://lore.kernel.org/git/pull.845.git.1614484707.gitgitgadget@gmail.com/;
there are five more waiting after that -- viewable by the curious at
https://github.com/gitgitgadget/git/pulls?q=is%3Apr+author%3Anewren+Optimization+batch

Elijah Newren (11):
  merge-ort: use STABLE_QSORT instead of QSORT where required
  merge-ort: add a special minimal index just for renormalization
  merge-ort: add a function for initializing our special attr_index
  merge-ort: have ll_merge() calls use the attr_index for
    renormalization
  merge-ort: let renormalization change modify/delete into clean delete
  merge-ort: support subtree shifting
  t6428: new test for SKIP_WORKTREE handling and conflicts
  merge-ort: implement CE_SKIP_WORKTREE handling with conflicted entries
  t: mark several submodule merging tests as fixed under merge-ort
  merge-ort: write $GIT_DIR/AUTO_MERGE whenever we hit a conflict
  merge-recursive: add a bunch of FIXME comments documenting known bugs

 branch.c                                      |   1 +
 builtin/rebase.c                              |   1 +
 merge-ort.c                                   | 230 ++++++++++++++++--
 merge-recursive.c                             |  37 +++
 path.c                                        |   1 +
 path.h                                        |   2 +
 sequencer.c                                   |   5 +
 t/t3512-cherry-pick-submodule.sh              |   9 +-
 t/t3513-revert-submodule.sh                   |   7 +-
 t/t5572-pull-submodule.sh                     |   9 +-
 t/t6428-merge-conflicts-sparse.sh             | 158 ++++++++++++
 t/t6437-submodule-merge.sh                    |   5 +-
 t/t6438-submodule-directory-file-conflicts.sh |   9 +-
 13 files changed, 449 insertions(+), 25 deletions(-)
 create mode 100755 t/t6428-merge-conflicts-sparse.sh

base-commit: f01623b2c9d14207e497b21ebc6b3ec4afaf4b46

Submitted-As: https://lore.kernel.org/git/pull.973.git.git.1614905738.gitgitgadget@gmail.com