[PATCH v3 0/8] Debug merge-recursive.[ch]

Changes since v1:

 * fixed a couple of typos in commit messages

Changes since v2.

 * clarified the commit message for patch 6, and the cover letter

Clarified cover letter:

As a wise man once told me, "Deleted code is debugged code!"

This series does some preparation, then moves the code shared between merge-recursive and merge-ort from the former to the latter, and then "debugs" the remainder of merge-recursive.[ch].

Joking aside, merge-ort was always intended to replace merge-recursive. It did replace it as the default years ago in commit 6a5fb966720f (Change default merge backend from recursive to ort, 2021-08-04), and was noted to be better on correctness, extensibility, and performance issues. In this series, we convert the remaining callers of merge-recursive over to merge-ort equivalents, move the shared code between merge-recursive and merge-ort from the former to the latter, and then delete the remainder of merge-recursive.[ch] as it has now been fully replaced. We then clean up some test framework scaffolding that was put into place to allow us to reuse the recursive tests as ort tests.

Series overview:

 * Patches 1-5: Preparation; switch remaining callers of
   merge-recursive.[ch] functions to merge-ort equivalents, and add sole
   remaining missing feature (diff-algorithm selection)
 * Patch 6: Nuke merge-recursive.[ch]
 * Patch 7-8: Cleanup testsuite; we don't need GIT_TEST_MERGE_ALGORITHM
   anymore

While the diffstat might look large, the non-test code changes are actually pretty small. The drivers of the big diffstat are:

 * We move a significant chunk of shared code from merge-recursive.[ch] to
   merge-ort.[ch], without modifying it
 * We delete (the remainder of) merge-recursive.[ch]
 * We rip out all the temporary GIT_TEST_MERGE_ALGORITHM stuff designed to
   let us reuse tests between recursive and ort

Elijah Newren (8):
  checkout: replace merge_trees() with merge_ort_nonrecursive()
  builtin/merge-recursive: switch to using merge_ort_generic()
  merge-ort: enable diff-algorithms other than histogram
  sequencer: switch non-recursive merges over to ort
  merge, sequencer: switch recursive merges over to ort
  merge-recursive.[ch]: thoroughly debug these
  tests: remove GIT_TEST_MERGE_ALGORITHM and test_expect_merge_algorithm
  builtin/{merge,rebase,revert}: remove GIT_TEST_MERGE_ALGORITHM

 Documentation/merge-strategies.adoc           |   51 +-
 Documentation/technical/sparse-checkout.adoc  |    2 -
 Makefile                                      |    1 -
 builtin/checkout.c                            |   10 +-
 builtin/merge-recursive.c                     |    4 +-
 builtin/merge.c                               |   23 +-
 builtin/rebase.c                              |    5 -
 builtin/revert.c                              |    2 -
 ci/run-build-and-tests.sh                     |    1 -
 merge-ort-wrappers.h                          |    2 +-
 merge-ort.c                                   |  162 +-
 merge-ort.h                                   |   60 +-
 merge-recursive.c                             | 4079 -----------------
 merge-recursive.h                             |  132 -
 meson.build                                   |    1 -
 sequencer.c                                   |   58 +-
 t/lib-merge.sh                                |   13 -
 t/t1092-sparse-checkout-compatibility.sh      |    2 -
 t/t2501-cwd-empty.sh                          |    2 -
 t/t3512-cherry-pick-submodule.sh              |    5 -
 t/t3513-revert-submodule.sh                   |    4 -
 t/t4069-remerge-diff.sh                       |    7 -
 t/t4301-merge-tree-write-tree.sh              |    7 -
 t/t5572-pull-submodule.sh                     |    5 -
 t/t6400-merge-df.sh                           |   14 +-
 t/t6402-merge-rename.sh                       |  125 +-
 t/t6404-recursive-merge.sh                    |   21 +-
 t/t6406-merge-attr.sh                         |    7 +-
 t/t6416-recursive-corner-cases.sh             |  194 +-
 t/t6421-merge-partial-clone.sh                |    7 +-
 t/t6422-merge-rename-corner-cases.sh          |   31 +-
 t/t6423-merge-rename-directories.sh           |  517 +--
 t/t6424-merge-unrelated-index-changes.sh      |    8 +-
 t/t6426-merge-skip-unneeded-updates.sh        |    4 +-
 t/t6428-merge-conflicts-sparse.sh             |    2 -
 t/t6430-merge-recursive.sh                    |   46 +-
 t/t6434-merge-recursive-rename-options.sh     |   16 +-
 t/t6436-merge-overwrite.sh                    |   17 +-
 t/t6437-submodule-merge.sh                    |   65 +-
 t/t6438-submodule-directory-file-conflicts.sh |    5 -
 t/t6439-merge-co-error-msgs.sh                |    2 +-
 t/t7402-submodule-rebase.sh                   |    7 +-
 t/t7602-merge-octopus-many.sh                 |    9 +-
 t/t7610-mergetool.sh                          |   40 +-
 t/t7615-diff-algo-with-mergy-operations.sh    |    2 -
 t/test-lib.sh                                 |    2 -
 46 files changed, 538 insertions(+), 5241 deletions(-)
 delete mode 100644 merge-recursive.c
 delete mode 100644 merge-recursive.h
 delete mode 100644 t/lib-merge.sh

base-commit: 5b97a56fa0e7d580dc8865b73107407c9b3f0eff
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1898%2Fnewren%2Fendit-quote-debugging-unquote-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1898/newren/endit-quote-debugging-unquote-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/1898

Range-diff vs v2:

 1:  0e150ee9065 = 1:  0e150ee9065 checkout: replace merge_trees() with merge_ort_nonrecursive()
 2:  b093d74968b = 2:  b093d74968b builtin/merge-recursive: switch to using merge_ort_generic()
 3:  cf774437123 = 3:  cf774437123 merge-ort: enable diff-algorithms other than histogram
 4:  6203589ac17 = 4:  6203589ac17 sequencer: switch non-recursive merges over to ort
 5:  8821f22d5ea = 5:  8821f22d5ea merge, sequencer: switch recursive merges over to ort
 6:  770f611c2b6 ! 6:  e696cb472bd merge-recursive.[ch]: thoroughly debug these
     @@ Commit message
          the former to the latter, and then debug the remainder of
          merge-recursive.[ch].
      
     +    Joking aside, merge-ort was always intended to replace merge-recursive.
     +    It has numerous advantages over merge-recursive (operates much faster,
     +    can operate without a worktree or index, and fixes a number of known
     +    bugs and suboptimal merges).  Since we have now replaced all callers of
     +    merge-recursive with equivalent functions from merge-ort, move the
     +    shared functions from the former to the latter, and delete the remainder
     +    of merge-recursive.[ch].
     +
          Signed-off-by: Elijah Newren <newren@gmail.com>
      
       ## Documentation/merge-strategies.adoc ##
 7:  a6501ee85fa = 7:  5dce9096e23 tests: remove GIT_TEST_MERGE_ALGORITHM and test_expect_merge_algorithm
 8:  d1dea986646 = 8:  bf2d462c4e5 builtin/{merge,rebase,revert}: remove GIT_TEST_MERGE_ALGORITHM