[PATCH v2 0/8] Debug merge-recursive.[ch]

Changes since v1:

 * fixed a couple of typos in commit messages

Original 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].

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-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1898/newren/endit-quote-debugging-unquote-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/1898

Range-diff vs v1:

 1:  0e150ee9065 = 1:  0e150ee9065 checkout: replace merge_trees() with merge_ort_nonrecursive()
 2:  44be41da6c5 ! 2:  b093d74968b builtin/merge-recursive: switch to using merge_ort_generic()
     @@ Commit message
            adaptation from merge_recursive_internal(); see 8119214f4e70
            (merge-ort: implement merge_incore_recursive(), 2020-12-16).
      
     -    * t6436: This test is built entirely around rename/delete conflicts,
     +    * t6434: This test is built entirely around rename/delete conflicts,
            which had a suboptimal handling under merge-recursive.  As explained
            in more detail in commits 1f3c9ba707 ("t6425: be more flexible with
            rename/delete conflict messages", 2020-08-10) and 727c75b23f ("t6404,
 3:  3945c471b0c = 3:  cf774437123 merge-ort: enable diff-algorithms other than histogram
 4:  39ff4860fcd = 4:  6203589ac17 sequencer: switch non-recursive merges over to ort
 5:  91398ffd1e1 = 5:  8821f22d5ea merge, sequencer: switch recursive merges over to ort
 6:  6ef536cdbcd = 6:  770f611c2b6 merge-recursive.[ch]: thoroughly debug these
 7:  0b6bcd225dc ! 7:  a6501ee85fa tests: remove GIT_TEST_MERGE_ALGORITHM and test_expect_merge_algorithm
     @@ Metadata
       ## Commit message ##
          tests: remove GIT_TEST_MERGE_ALGORITHM and test_expect_merge_algorithm
      
     -    Both of these existed to allow use to reuse all the merge-related tests
     +    Both of these existed to allow us to reuse all the merge-related tests
          in the testsuite while easily flipping between the 'recursive' and the
          'ort' backends.  Now that we have removed merge-recursive and remapped
          'recursive' to mean 'ort', we don't need this scaffolding anymore.
 8:  3abcfe6faf0 = 8:  d1dea986646 builtin/{merge,rebase,revert}: remove GIT_TEST_MERGE_ALGORITHM