The switch to diff3 by default got stuck on a tar pit, however that's no
reason not to improve the merge.conflictStyle handling.

I dropped all the controversial changes and focused only on the obvious
improvements.

I switched to from the custom fill function to test_write_lines as Eric
Sunshine suggested, and used a simpler and stricter grep regex for diff3
markers as Phillip Wood prompted.

Felipe Contreras (4):
  test: add merge style config test
  merge-tree: fix merge.conflictstyle handling
  notes: fix merge.conflictstyle handling
  test: document broken merge.conflictStyle handling

 builtin/merge-tree.c               |   4 +
 builtin/notes.c                    |   3 +-
 t/t6440-config-conflict-markers.sh | 116 +++++++++++++++++++++++++++++
 3 files changed, 122 insertions(+), 1 deletion(-)
 create mode 100755 t/t6440-config-conflict-markers.sh

Range-diff against v1:
1:  118388c313 ! 1:  51351f1a77 test: add merge style config test
    @@ t/t6440-config-conflict-markers.sh (new)
     +
     +. ./test-lib.sh
     +
    -+fill () {
    -+	for i
    -+	do
    -+		echo "$i"
    -+	done
    -+}
    -+
     +test_expect_success 'merge' '
     +	test_create_repo merge &&
     +	(
     +		cd merge &&
     +
    -+		fill 1 2 3 >content &&
    ++		test_write_lines 1 2 3 >content &&
     +		git add content &&
     +		git commit -m base &&
     +
    @@ t/t6440-config-conflict-markers.sh (new)
     +		git commit -a -m left &&
     +
     +		test_must_fail git merge r &&
    -+		! grep -E "\|+" content &&
    ++		! grep "^|||||||" content &&
     +
     +		git reset --hard &&
     +		test_must_fail git -c merge.conflictstyle=diff3 merge r &&
    -+		grep -E "\|+" content &&
    ++		grep "^|||||||" content &&
     +
     +		git reset --hard &&
     +		test_must_fail git -c merge.conflictstyle=merge merge r &&
    -+		! grep -E "\|+" content
    ++		! grep "^|||||||" content
     +	)
     +'
     +
2:  697f2a2a5c ! 2:  1fccf561ed merge-tree: fix merge.conflictstyle handling
    @@ t/t6440-config-conflict-markers.sh: test_expect_success 'merge' '
     +		test_commit l content l &&
     +
     +		git merge-tree initial r l >actual &&
    -+		! grep -E "\|+" actual &&
    ++		! grep "^+|||||||" content &&
     +
     +		git -c merge.conflictstyle=diff3 merge-tree initial r l >actual &&
    -+		grep -E "\|+" actual &&
    ++		grep "^+|||||||" actual &&
     +
     +		git -c merge.conflictstyle=merge merge-tree initial r l >actual &&
    -+		! grep -E "\|+" actual
    ++		! grep "^+|||||||" content
     +	)
     +'
     +
3:  56a20f41a4 ! 3:  3bb872e3cd notes: fix merge.conflictstyle handling
    @@ t/t6440-config-conflict-markers.sh: test_expect_success 'merge-tree' '
     +		git notes add -f -m l initial &&
     +
     +		test_must_fail git notes merge r &&
    -+		! grep -E "\|+" .git/NOTES_MERGE_WORKTREE/* &&
    ++		! grep "^|||||||" .git/NOTES_MERGE_WORKTREE/* &&
     +
     +		git notes merge --abort &&
     +		test_must_fail git -c merge.conflictstyle=diff3 notes merge r &&
    -+		grep -E "\|+" .git/NOTES_MERGE_WORKTREE/* &&
    ++		grep "^|||||||" .git/NOTES_MERGE_WORKTREE/* &&
     +
     +		git notes merge --abort &&
     +		test_must_fail git -c merge.conflictstyle=merge notes merge r &&
    -+		! grep -E "\|+" .git/NOTES_MERGE_WORKTREE/*
    ++		! grep "^|||||||" .git/NOTES_MERGE_WORKTREE/*
     +	)
     +'
     +
4:  adce598754 < -:  ---------- checkout: fix merge.conflictstyle handling
5:  a4ddbbc44a < -:  ---------- xdiff: rename XDL_MERGE_STYLE_DIFF3
6:  c3e0940dab < -:  ---------- xdiff: simplify style assignments
7:  6415e53345 < -:  ---------- xdiff: make diff3 the default conflictStyle
-:  ---------- > 4:  a767bc68e6 test: document broken merge.conflictStyle handling
-- 
2.32.0