merge(third_party/git): Merge squashed git subtree at v2.23.0 r/373

Merge commit '1b593e1ea4d2af0f6444d9a7788d5d99abd6fde5' as 'third_party/git'

1 files changed, 735 insertions, 0 deletions

diff --git a/third_party/git/t/t3030-merge-recursive.sh b/third_party/git/t/t3030-merge-recursive.sh
new file mode 100755
index 000000000000..ff641b348a1b
--- /dev/null
+++ b/third_party/git/t/t3030-merge-recursive.sh
@@ -0,0 +1,735 @@
+#!/bin/sh
+
+test_description='merge-recursive backend test'
+
+. ./test-lib.sh
+
+test_expect_success 'setup 1' '
+
+	echo hello >a &&
+	o0=$(git hash-object a) &&
+	cp a b &&
+	cp a c &&
+	mkdir d &&
+	cp a d/e &&
+
+	test_tick &&
+	git add a b c d/e &&
+	git commit -m initial &&
+	c0=$(git rev-parse --verify HEAD) &&
+	git branch side &&
+	git branch df-1 &&
+	git branch df-2 &&
+	git branch df-3 &&
+	git branch remove &&
+	git branch submod &&
+	git branch copy &&
+	git branch rename &&
+	git branch rename-ln &&
+
+	echo hello >>a &&
+	cp a d/e &&
+	o1=$(git hash-object a) &&
+
+	git add a d/e &&
+
+	test_tick &&
+	git commit -m "master modifies a and d/e" &&
+	c1=$(git rev-parse --verify HEAD) &&
+	( git ls-tree -r HEAD && git ls-files -s ) >actual &&
+	(
+		echo "100644 blob $o1	a" &&
+		echo "100644 blob $o0	b" &&
+		echo "100644 blob $o0	c" &&
+		echo "100644 blob $o1	d/e" &&
+		echo "100644 $o1 0	a" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o1 0	d/e"
+	) >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'setup 2' '
+
+	rm -rf [abcd] &&
+	git checkout side &&
+	( git ls-tree -r HEAD && git ls-files -s ) >actual &&
+	(
+		echo "100644 blob $o0	a" &&
+		echo "100644 blob $o0	b" &&
+		echo "100644 blob $o0	c" &&
+		echo "100644 blob $o0	d/e" &&
+		echo "100644 $o0 0	a" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o0 0	d/e"
+	) >expected &&
+	test_cmp expected actual &&
+
+	echo goodbye >>a &&
+	o2=$(git hash-object a) &&
+
+	git add a &&
+
+	test_tick &&
+	git commit -m "side modifies a" &&
+	c2=$(git rev-parse --verify HEAD) &&
+	( git ls-tree -r HEAD && git ls-files -s ) >actual &&
+	(
+		echo "100644 blob $o2	a" &&
+		echo "100644 blob $o0	b" &&
+		echo "100644 blob $o0	c" &&
+		echo "100644 blob $o0	d/e" &&
+		echo "100644 $o2 0	a" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o0 0	d/e"
+	) >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'setup 3' '
+
+	rm -rf [abcd] &&
+	git checkout df-1 &&
+	( git ls-tree -r HEAD && git ls-files -s ) >actual &&
+	(
+		echo "100644 blob $o0	a" &&
+		echo "100644 blob $o0	b" &&
+		echo "100644 blob $o0	c" &&
+		echo "100644 blob $o0	d/e" &&
+		echo "100644 $o0 0	a" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o0 0	d/e"
+	) >expected &&
+	test_cmp expected actual &&
+
+	rm -f b && mkdir b && echo df-1 >b/c && git add b/c &&
+	o3=$(git hash-object b/c) &&
+
+	test_tick &&
+	git commit -m "df-1 makes b/c" &&
+	c3=$(git rev-parse --verify HEAD) &&
+	( git ls-tree -r HEAD && git ls-files -s ) >actual &&
+	(
+		echo "100644 blob $o0	a" &&
+		echo "100644 blob $o3	b/c" &&
+		echo "100644 blob $o0	c" &&
+		echo "100644 blob $o0	d/e" &&
+		echo "100644 $o0 0	a" &&
+		echo "100644 $o3 0	b/c" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o0 0	d/e"
+	) >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'setup 4' '
+
+	rm -rf [abcd] &&
+	git checkout df-2 &&
+	( git ls-tree -r HEAD && git ls-files -s ) >actual &&
+	(
+		echo "100644 blob $o0	a" &&
+		echo "100644 blob $o0	b" &&
+		echo "100644 blob $o0	c" &&
+		echo "100644 blob $o0	d/e" &&
+		echo "100644 $o0 0	a" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o0 0	d/e"
+	) >expected &&
+	test_cmp expected actual &&
+
+	rm -f a && mkdir a && echo df-2 >a/c && git add a/c &&
+	o4=$(git hash-object a/c) &&
+
+	test_tick &&
+	git commit -m "df-2 makes a/c" &&
+	c4=$(git rev-parse --verify HEAD) &&
+	( git ls-tree -r HEAD && git ls-files -s ) >actual &&
+	(
+		echo "100644 blob $o4	a/c" &&
+		echo "100644 blob $o0	b" &&
+		echo "100644 blob $o0	c" &&
+		echo "100644 blob $o0	d/e" &&
+		echo "100644 $o4 0	a/c" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o0 0	d/e"
+	) >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'setup 5' '
+
+	rm -rf [abcd] &&
+	git checkout remove &&
+	( git ls-tree -r HEAD && git ls-files -s ) >actual &&
+	(
+		echo "100644 blob $o0	a" &&
+		echo "100644 blob $o0	b" &&
+		echo "100644 blob $o0	c" &&
+		echo "100644 blob $o0	d/e" &&
+		echo "100644 $o0 0	a" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o0 0	d/e"
+	) >expected &&
+	test_cmp expected actual &&
+
+	rm -f b &&
+	echo remove-conflict >a &&
+
+	git add a &&
+	git rm b &&
+	o5=$(git hash-object a) &&
+
+	test_tick &&
+	git commit -m "remove removes b and modifies a" &&
+	c5=$(git rev-parse --verify HEAD) &&
+	( git ls-tree -r HEAD && git ls-files -s ) >actual &&
+	(
+		echo "100644 blob $o5	a" &&
+		echo "100644 blob $o0	c" &&
+		echo "100644 blob $o0	d/e" &&
+		echo "100644 $o5 0	a" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o0 0	d/e"
+	) >expected &&
+	test_cmp expected actual
+
+'
+
+test_expect_success 'setup 6' '
+
+	rm -rf [abcd] &&
+	git checkout df-3 &&
+	( git ls-tree -r HEAD && git ls-files -s ) >actual &&
+	(
+		echo "100644 blob $o0	a" &&
+		echo "100644 blob $o0	b" &&
+		echo "100644 blob $o0	c" &&
+		echo "100644 blob $o0	d/e" &&
+		echo "100644 $o0 0	a" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o0 0	d/e"
+	) >expected &&
+	test_cmp expected actual &&
+
+	rm -fr d && echo df-3 >d && git add d &&
+	o6=$(git hash-object d) &&
+
+	test_tick &&
+	git commit -m "df-3 makes d" &&
+	c6=$(git rev-parse --verify HEAD) &&
+	( git ls-tree -r HEAD && git ls-files -s ) >actual &&
+	(
+		echo "100644 blob $o0	a" &&
+		echo "100644 blob $o0	b" &&
+		echo "100644 blob $o0	c" &&
+		echo "100644 blob $o6	d" &&
+		echo "100644 $o0 0	a" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o6 0	d"
+	) >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'setup 7' '
+
+	git checkout submod &&
+	git rm d/e &&
+	test_tick &&
+	git commit -m "remove d/e" &&
+	git update-index --add --cacheinfo 160000 $c1 d &&
+	test_tick &&
+	git commit -m "make d/ a submodule"
+'
+
+test_expect_success 'setup 8' '
+	git checkout rename &&
+	git mv a e &&
+	git add e &&
+	test_tick &&
+	git commit -m "rename a->e" &&
+	c7=$(git rev-parse --verify HEAD) &&
+	git checkout rename-ln &&
+	git mv a e &&
+	test_ln_s_add e a &&
+	test_tick &&
+	git commit -m "rename a->e, symlink a->e" &&
+	oln=$(printf e | git hash-object --stdin)
+'
+
+test_expect_success 'setup 9' '
+	git checkout copy &&
+	cp a e &&
+	git add e &&
+	test_tick &&
+	git commit -m "copy a->e"
+'
+
+test_expect_success 'merge-recursive simple' '
+
+	rm -fr [abcd] &&
+	git checkout -f "$c2" &&
+
+	test_expect_code 1 git merge-recursive "$c0" -- "$c2" "$c1"
+'
+
+test_expect_success 'merge-recursive result' '
+
+	git ls-files -s >actual &&
+	(
+		echo "100644 $o0 1	a" &&
+		echo "100644 $o2 2	a" &&
+		echo "100644 $o1 3	a" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o1 0	d/e"
+	) >expected &&
+	test_cmp expected actual
+
+'
+
+test_expect_success 'fail if the index has unresolved entries' '
+
+	rm -fr [abcd] &&
+	git checkout -f "$c1" &&
+
+	test_must_fail git merge "$c5" &&
+	test_must_fail git merge "$c5" 2> out &&
+	test_i18ngrep "not possible because you have unmerged files" out &&
+	git add -u &&
+	test_must_fail git merge "$c5" 2> out &&
+	test_i18ngrep "You have not concluded your merge" out &&
+	rm -f .git/MERGE_HEAD &&
+	test_must_fail git merge "$c5" 2> out &&
+	test_i18ngrep "Your local changes to the following files would be overwritten by merge:" out
+'
+
+test_expect_success 'merge-recursive remove conflict' '
+
+	rm -fr [abcd] &&
+	git checkout -f "$c1" &&
+
+	test_expect_code 1 git merge-recursive "$c0" -- "$c1" "$c5"
+'
+
+test_expect_success 'merge-recursive remove conflict' '
+
+	git ls-files -s >actual &&
+	(
+		echo "100644 $o0 1	a" &&
+		echo "100644 $o1 2	a" &&
+		echo "100644 $o5 3	a" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o1 0	d/e"
+	) >expected &&
+	test_cmp expected actual
+
+'
+
+test_expect_success 'merge-recursive d/f simple' '
+	rm -fr [abcd] &&
+	git reset --hard &&
+	git checkout -f "$c1" &&
+
+	git merge-recursive "$c0" -- "$c1" "$c3"
+'
+
+test_expect_success 'merge-recursive result' '
+
+	git ls-files -s >actual &&
+	(
+		echo "100644 $o1 0	a" &&
+		echo "100644 $o3 0	b/c" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o1 0	d/e"
+	) >expected &&
+	test_cmp expected actual
+
+'
+
+test_expect_success 'merge-recursive d/f conflict' '
+
+	rm -fr [abcd] &&
+	git reset --hard &&
+	git checkout -f "$c1" &&
+
+	test_expect_code 1 git merge-recursive "$c0" -- "$c1" "$c4"
+'
+
+test_expect_success 'merge-recursive d/f conflict result' '
+
+	git ls-files -s >actual &&
+	(
+		echo "100644 $o0 1	a" &&
+		echo "100644 $o1 2	a" &&
+		echo "100644 $o4 0	a/c" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o1 0	d/e"
+	) >expected &&
+	test_cmp expected actual
+
+'
+
+test_expect_success 'merge-recursive d/f conflict the other way' '
+
+	rm -fr [abcd] &&
+	git reset --hard &&
+	git checkout -f "$c4" &&
+
+	test_expect_code 1 git merge-recursive "$c0" -- "$c4" "$c1"
+'
+
+test_expect_success 'merge-recursive d/f conflict result the other way' '
+
+	git ls-files -s >actual &&
+	(
+		echo "100644 $o0 1	a" &&
+		echo "100644 $o1 3	a" &&
+		echo "100644 $o4 0	a/c" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o1 0	d/e"
+	) >expected &&
+	test_cmp expected actual
+
+'
+
+test_expect_success 'merge-recursive d/f conflict' '
+
+	rm -fr [abcd] &&
+	git reset --hard &&
+	git checkout -f "$c1" &&
+
+	test_expect_code 1 git merge-recursive "$c0" -- "$c1" "$c6"
+'
+
+test_expect_success 'merge-recursive d/f conflict result' '
+
+	git ls-files -s >actual &&
+	(
+		echo "100644 $o1 0	a" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o6 3	d" &&
+		echo "100644 $o0 1	d/e" &&
+		echo "100644 $o1 2	d/e"
+	) >expected &&
+	test_cmp expected actual
+
+'
+
+test_expect_success 'merge-recursive d/f conflict' '
+
+	rm -fr [abcd] &&
+	git reset --hard &&
+	git checkout -f "$c6" &&
+
+	test_expect_code 1 git merge-recursive "$c0" -- "$c6" "$c1"
+'
+
+test_expect_success 'merge-recursive d/f conflict result' '
+
+	git ls-files -s >actual &&
+	(
+		echo "100644 $o1 0	a" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o6 2	d" &&
+		echo "100644 $o0 1	d/e" &&
+		echo "100644 $o1 3	d/e"
+	) >expected &&
+	test_cmp expected actual
+
+'
+
+test_expect_success 'reset and 3-way merge' '
+
+	git reset --hard "$c2" &&
+	git read-tree -m "$c0" "$c2" "$c1"
+
+'
+
+test_expect_success 'reset and bind merge' '
+
+	git reset --hard master &&
+	git read-tree --prefix=M/ master &&
+	git ls-files -s >actual &&
+	(
+		echo "100644 $o1 0	M/a" &&
+		echo "100644 $o0 0	M/b" &&
+		echo "100644 $o0 0	M/c" &&
+		echo "100644 $o1 0	M/d/e" &&
+		echo "100644 $o1 0	a" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o1 0	d/e"
+	) >expected &&
+	test_cmp expected actual &&
+
+	git read-tree --prefix=a1/ master &&
+	git ls-files -s >actual &&
+	(
+		echo "100644 $o1 0	M/a" &&
+		echo "100644 $o0 0	M/b" &&
+		echo "100644 $o0 0	M/c" &&
+		echo "100644 $o1 0	M/d/e" &&
+		echo "100644 $o1 0	a" &&
+		echo "100644 $o1 0	a1/a" &&
+		echo "100644 $o0 0	a1/b" &&
+		echo "100644 $o0 0	a1/c" &&
+		echo "100644 $o1 0	a1/d/e" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o1 0	d/e"
+	) >expected &&
+	test_cmp expected actual &&
+
+	git read-tree --prefix=z/ master &&
+	git ls-files -s >actual &&
+	(
+		echo "100644 $o1 0	M/a" &&
+		echo "100644 $o0 0	M/b" &&
+		echo "100644 $o0 0	M/c" &&
+		echo "100644 $o1 0	M/d/e" &&
+		echo "100644 $o1 0	a" &&
+		echo "100644 $o1 0	a1/a" &&
+		echo "100644 $o0 0	a1/b" &&
+		echo "100644 $o0 0	a1/c" &&
+		echo "100644 $o1 0	a1/d/e" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o1 0	d/e" &&
+		echo "100644 $o1 0	z/a" &&
+		echo "100644 $o0 0	z/b" &&
+		echo "100644 $o0 0	z/c" &&
+		echo "100644 $o1 0	z/d/e"
+	) >expected &&
+	test_cmp expected actual
+
+'
+
+test_expect_success 'merge-recursive w/ empty work tree - ours has rename' '
+	(
+		GIT_WORK_TREE="$PWD/ours-has-rename-work" &&
+		export GIT_WORK_TREE &&
+		GIT_INDEX_FILE="$PWD/ours-has-rename-index" &&
+		export GIT_INDEX_FILE &&
+		mkdir "$GIT_WORK_TREE" &&
+		git read-tree -i -m $c7 2>actual-err &&
+		test_must_be_empty actual-err &&
+		git update-index --ignore-missing --refresh 2>actual-err &&
+		test_must_be_empty actual-err &&
+		git merge-recursive $c0 -- $c7 $c3 2>actual-err &&
+		test_must_be_empty actual-err &&
+		git ls-files -s >actual-files 2>actual-err &&
+		test_must_be_empty actual-err
+	) &&
+	cat >expected-files <<-EOF &&
+	100644 $o3 0	b/c
+	100644 $o0 0	c
+	100644 $o0 0	d/e
+	100644 $o0 0	e
+	EOF
+	test_cmp expected-files actual-files
+'
+
+test_expect_success 'merge-recursive w/ empty work tree - theirs has rename' '
+	(
+		GIT_WORK_TREE="$PWD/theirs-has-rename-work" &&
+		export GIT_WORK_TREE &&
+		GIT_INDEX_FILE="$PWD/theirs-has-rename-index" &&
+		export GIT_INDEX_FILE &&
+		mkdir "$GIT_WORK_TREE" &&
+		git read-tree -i -m $c3 2>actual-err &&
+		test_must_be_empty actual-err &&
+		git update-index --ignore-missing --refresh 2>actual-err &&
+		test_must_be_empty actual-err &&
+		git merge-recursive $c0 -- $c3 $c7 2>actual-err &&
+		test_must_be_empty actual-err &&
+		git ls-files -s >actual-files 2>actual-err &&
+		test_must_be_empty actual-err
+	) &&
+	cat >expected-files <<-EOF &&
+	100644 $o3 0	b/c
+	100644 $o0 0	c
+	100644 $o0 0	d/e
+	100644 $o0 0	e
+	EOF
+	test_cmp expected-files actual-files
+'
+
+test_expect_success 'merge removes empty directories' '
+
+	git reset --hard master &&
+	git checkout -b rm &&
+	git rm d/e &&
+	git commit -mremoved-d/e &&
+	git checkout master &&
+	git merge -s recursive rm &&
+	test_must_fail test -d d
+'
+
+test_expect_success 'merge-recursive simple w/submodule' '
+
+	git checkout submod &&
+	git merge remove
+'
+
+test_expect_success 'merge-recursive simple w/submodule result' '
+
+	git ls-files -s >actual &&
+	(
+		echo "100644 $o5 0	a" &&
+		echo "100644 $o0 0	c" &&
+		echo "160000 $c1 0	d"
+	) >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'merge-recursive copy vs. rename' '
+	git checkout -f copy &&
+	git merge rename &&
+	( git ls-tree -r HEAD && git ls-files -s ) >actual &&
+	(
+		echo "100644 blob $o0	b" &&
+		echo "100644 blob $o0	c" &&
+		echo "100644 blob $o0	d/e" &&
+		echo "100644 blob $o0	e" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o0 0	d/e" &&
+		echo "100644 $o0 0	e"
+	) >expected &&
+	test_cmp expected actual
+'
+
+test_expect_failure 'merge-recursive rename vs. rename/symlink' '
+
+	git checkout -f rename &&
+	git merge rename-ln &&
+	( git ls-tree -r HEAD && git ls-files -s ) >actual &&
+	(
+		echo "120000 blob $oln	a" &&
+		echo "100644 blob $o0	b" &&
+		echo "100644 blob $o0	c" &&
+		echo "100644 blob $o0	d/e" &&
+		echo "100644 blob $o0	e" &&
+		echo "120000 $oln 0	a" &&
+		echo "100644 $o0 0	b" &&
+		echo "100644 $o0 0	c" &&
+		echo "100644 $o0 0	d/e" &&
+		echo "100644 $o0 0	e"
+	) >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'merging with triple rename across D/F conflict' '
+	git reset --hard HEAD &&
+	git checkout -b main &&
+	git rm -rf . &&
+
+	echo "just a file" >sub1 &&
+	mkdir -p sub2 &&
+	echo content1 >sub2/file1 &&
+	echo content2 >sub2/file2 &&
+	echo content3 >sub2/file3 &&
+	mkdir simple &&
+	echo base >simple/bar &&
+	git add -A &&
+	test_tick &&
+	git commit -m base &&
+
+	git checkout -b other &&
+	echo more >>simple/bar &&
+	test_tick &&
+	git commit -a -m changesimplefile &&
+
+	git checkout main &&
+	git rm sub1 &&
+	git mv sub2 sub1 &&
+	test_tick &&
+	git commit -m changefiletodir &&
+
+	test_tick &&
+	git merge other
+'
+
+test_expect_success 'merge-recursive remembers the names of all base trees' '
+	git reset --hard HEAD &&
+
+	# more trees than static slots used by oid_to_hex()
+	for commit in $c0 $c2 $c4 $c5 $c6 $c7
+	do
+		git rev-parse "$commit^{tree}"
+	done >trees &&
+
+	# ignore the return code -- it only fails because the input is weird
+	test_must_fail git -c merge.verbosity=5 merge-recursive $(cat trees) -- $c1 $c3 >out &&
+
+	# merge-recursive prints in reverse order, but we do not care
+	sort <trees >expect &&
+	sed -n "s/^virtual //p" out | sort >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'merge-recursive internal merge resolves to the sameness' '
+	git reset --hard HEAD &&
+
+	# We are going to create a history leading to two criss-cross
+	# branches A and B.  The common ancestor at the bottom, O0,
+	# has two child commits O1 and O2, both of which will be merge
+	# base between A and B, like so:
+	#
+	#       O1---A
+	#      /  \ /
+	#    O0    .
+	#      \  / \
+	#       O2---B
+	#
+	# The recently added "check to see if the index is different from
+	# the tree into which something else is getting merged" check must
+	# NOT kick in when an inner merge between O1 and O2 is made.  Both
+	# O1 and O2 happen to have the same tree as O0 in this test to
+	# trigger the bug---whether the inner merge is made by merging O2
+	# into O1 or O1 into O2, their common ancestor O0 and the branch
+	# being merged have the same tree.  We should not trigger the "is
+	# the index dirty?" check in this case.
+
+	echo "zero" >file &&
+	git add file &&
+	test_tick &&
+	git commit -m "O0" &&
+	O0=$(git rev-parse HEAD) &&
+
+	test_tick &&
+	git commit --allow-empty -m "O1" &&
+	O1=$(git rev-parse HEAD) &&
+
+	git reset --hard $O0 &&
+	test_tick &&
+	git commit --allow-empty -m "O2" &&
+	O2=$(git rev-parse HEAD) &&
+
+	test_tick &&
+	git merge -s ours $O1 &&
+	B=$(git rev-parse HEAD) &&
+
+	git reset --hard $O1 &&
+	test_tick &&
+	git merge -s ours $O2 &&
+	A=$(git rev-parse HEAD) &&
+
+	git merge $B
+'
+
+test_done