Merge branch 'gc/recursive-fetch-with-unused-submodules'

When "git fetch --recurse-submodules" grabbed submodule commits
that would be needed to recursively check out newly fetched commits
in the superproject, it only paid attention to submodules that are
in the current checkout of the superproject.  We now do so for all
submodules that have been run "git submodule init" on.

* gc/recursive-fetch-with-unused-submodules:
  submodule: fix latent check_has_commit() bug
  fetch: fetch unpopulated, changed submodules
  submodule: move logic into fetch_task_create()
  submodule: extract get_fetch_task()
  submodule: store new submodule commits oid_array in a struct
  submodule: inline submodule_commits() into caller
  submodule: make static functions read submodules from commits
  t5526: create superproject commits with test helper
  t5526: stop asserting on stderr literally
  t5526: introduce test helper to assert on fetches

1 files changed, 414 insertions, 131 deletions

diff --git a/t/t5526-fetch-submodules.sh b/t/t5526-fetch-submodules.sh
index 840c89cc8b..43dada8544 100755
--- a/t/t5526-fetch-submodules.sh
+++ b/t/t5526-fetch-submodules.sh
@@ -10,33 +10,122 @@ export GIT_TEST_FATAL_REGISTER_SUBMODULE_ODB
 
 pwd=$(pwd)
 
-add_upstream_commit() {
+write_expected_sub () {
+	NEW_HEAD=$1 &&
+	SUPER_HEAD=$2 &&
+	cat >"$pwd/expect.err.sub" <<-EOF
+	Fetching submodule submodule${SUPER_HEAD:+ at commit $SUPER_HEAD}
+	From $pwd/submodule
+	   OLD_HEAD..$NEW_HEAD  sub        -> origin/sub
+	EOF
+}
+
+write_expected_sub2 () {
+	NEW_HEAD=$1 &&
+	SUPER_HEAD=$2 &&
+	cat >"$pwd/expect.err.sub2" <<-EOF
+	Fetching submodule submodule2${SUPER_HEAD:+ at commit $SUPER_HEAD}
+	From $pwd/submodule2
+	   OLD_HEAD..$NEW_HEAD  sub2       -> origin/sub2
+	EOF
+}
+
+write_expected_deep () {
+	NEW_HEAD=$1 &&
+	SUB_HEAD=$2 &&
+	cat >"$pwd/expect.err.deep" <<-EOF
+	Fetching submodule submodule/subdir/deepsubmodule${SUB_HEAD:+ at commit $SUB_HEAD}
+	From $pwd/deepsubmodule
+	   OLD_HEAD..$NEW_HEAD  deep       -> origin/deep
+	EOF
+}
+
+write_expected_super () {
+	NEW_HEAD=$1 &&
+	cat >"$pwd/expect.err.super" <<-EOF
+	From $pwd/.
+	   OLD_HEAD..$NEW_HEAD  super      -> origin/super
+	EOF
+}
+
+# For each submodule in the test setup, this creates a commit and writes
+# a file that contains the expected err if that new commit were fetched.
+# These output files get concatenated in the right order by
+# verify_fetch_result().
+add_submodule_commits () {
 	(
 		cd submodule &&
-		head1=$(git rev-parse --short HEAD) &&
 		echo new >> subfile &&
 		test_tick &&
 		git add subfile &&
 		git commit -m new subfile &&
-		head2=$(git rev-parse --short HEAD) &&
-		echo "Fetching submodule submodule" > ../expect.err &&
-		echo "From $pwd/submodule" >> ../expect.err &&
-		echo "   $head1..$head2  sub        -> origin/sub" >> ../expect.err
+		new_head=$(git rev-parse --short HEAD) &&
+		write_expected_sub $new_head
 	) &&
 	(
 		cd deepsubmodule &&
-		head1=$(git rev-parse --short HEAD) &&
 		echo new >> deepsubfile &&
 		test_tick &&
 		git add deepsubfile &&
 		git commit -m new deepsubfile &&
-		head2=$(git rev-parse --short HEAD) &&
-		echo "Fetching submodule submodule/subdir/deepsubmodule" >> ../expect.err
-		echo "From $pwd/deepsubmodule" >> ../expect.err &&
-		echo "   $head1..$head2  deep       -> origin/deep" >> ../expect.err
+		new_head=$(git rev-parse --short HEAD) &&
+		write_expected_deep $new_head
 	)
 }
 
+# For each superproject in the test setup, update its submodule, add the
+# submodule and create a new commit with the submodule change.
+#
+# This requires add_submodule_commits() to be called first, otherwise
+# the submodules will not have changed and cannot be "git add"-ed.
+add_superproject_commits () {
+	(
+		cd submodule &&
+		(
+			cd subdir/deepsubmodule &&
+			git fetch &&
+			git checkout -q FETCH_HEAD
+		) &&
+		git add subdir/deepsubmodule &&
+		git commit -m "new deep submodule"
+	) &&
+	git add submodule &&
+	git commit -m "new submodule" &&
+	super_head=$(git rev-parse --short HEAD) &&
+	sub_head=$(git -C submodule rev-parse --short HEAD) &&
+	write_expected_super $super_head &&
+	write_expected_sub $sub_head
+}
+
+# Verifies that the expected repositories were fetched. This is done by
+# concatenating the files expect.err.[super|sub|deep] in the correct
+# order and comparing it to the actual stderr.
+#
+# If a repo should not be fetched in the test, its corresponding
+# expect.err file should be rm-ed.
+verify_fetch_result () {
+	ACTUAL_ERR=$1 &&
+	rm -f expect.err.combined &&
+	if test -f expect.err.super
+	then
+		cat expect.err.super >>expect.err.combined
+	fi &&
+	if test -f expect.err.sub
+	then
+		cat expect.err.sub >>expect.err.combined
+	fi &&
+	if test -f expect.err.deep
+	then
+		cat expect.err.deep >>expect.err.combined
+	fi &&
+	if test -f expect.err.sub2
+	then
+		cat expect.err.sub2 >>expect.err.combined
+	fi &&
+	sed -e 's/[0-9a-f][0-9a-f]*\.\./OLD_HEAD\.\./' "$ACTUAL_ERR" >actual.err.cmp &&
+	test_cmp expect.err.combined actual.err.cmp
+}
+
 test_expect_success setup '
 	mkdir deepsubmodule &&
 	(
@@ -68,38 +157,38 @@ test_expect_success setup '
 '
 
 test_expect_success "fetch --recurse-submodules recurses into submodules" '
-	add_upstream_commit &&
+	add_submodule_commits &&
 	(
 		cd downstream &&
 		git fetch --recurse-submodules >../actual.out 2>../actual.err
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err actual.err
+	verify_fetch_result actual.err
 '
 
 test_expect_success "submodule.recurse option triggers recursive fetch" '
-	add_upstream_commit &&
+	add_submodule_commits &&
 	(
 		cd downstream &&
 		git -c submodule.recurse fetch >../actual.out 2>../actual.err
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err actual.err
+	verify_fetch_result actual.err
 '
 
 test_expect_success "fetch --recurse-submodules -j2 has the same output behaviour" '
-	add_upstream_commit &&
+	add_submodule_commits &&
 	(
 		cd downstream &&
 		GIT_TRACE="$TRASH_DIRECTORY/trace.out" git fetch --recurse-submodules -j2 2>../actual.err
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err actual.err &&
+	verify_fetch_result actual.err &&
 	grep "2 tasks" trace.out
 '
 
 test_expect_success "fetch alone only fetches superproject" '
-	add_upstream_commit &&
+	add_submodule_commits &&
 	(
 		cd downstream &&
 		git fetch >../actual.out 2>../actual.err
@@ -124,11 +213,11 @@ test_expect_success "using fetchRecurseSubmodules=true in .gitmodules recurses i
 		git fetch >../actual.out 2>../actual.err
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err actual.err
+	verify_fetch_result actual.err
 '
 
 test_expect_success "--no-recurse-submodules overrides .gitmodules config" '
-	add_upstream_commit &&
+	add_submodule_commits &&
 	(
 		cd downstream &&
 		git fetch --no-recurse-submodules >../actual.out 2>../actual.err
@@ -155,7 +244,7 @@ test_expect_success "--recurse-submodules overrides fetchRecurseSubmodules setti
 		git config --unset submodule.submodule.fetchRecurseSubmodules
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err actual.err
+	verify_fetch_result actual.err
 '
 
 test_expect_success "--quiet propagates to submodules" '
@@ -177,13 +266,13 @@ test_expect_success "--quiet propagates to parallel submodules" '
 '
 
 test_expect_success "--dry-run propagates to submodules" '
-	add_upstream_commit &&
+	add_submodule_commits &&
 	(
 		cd downstream &&
 		git fetch --recurse-submodules --dry-run >../actual.out 2>../actual.err
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err actual.err
+	verify_fetch_result actual.err
 '
 
 test_expect_success "Without --dry-run propagates to submodules" '
@@ -192,22 +281,22 @@ test_expect_success "Without --dry-run propagates to submodules" '
 		git fetch --recurse-submodules >../actual.out 2>../actual.err
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err actual.err
+	verify_fetch_result actual.err
 '
 
 test_expect_success "recurseSubmodules=true propagates into submodules" '
-	add_upstream_commit &&
+	add_submodule_commits &&
 	(
 		cd downstream &&
 		git config fetch.recurseSubmodules true &&
 		git fetch >../actual.out 2>../actual.err
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err actual.err
+	verify_fetch_result actual.err
 '
 
 test_expect_success "--recurse-submodules overrides config in submodule" '
-	add_upstream_commit &&
+	add_submodule_commits &&
 	(
 		cd downstream &&
 		(
@@ -217,11 +306,11 @@ test_expect_success "--recurse-submodules overrides config in submodule" '
 		git fetch --recurse-submodules >../actual.out 2>../actual.err
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err actual.err
+	verify_fetch_result actual.err
 '
 
 test_expect_success "--no-recurse-submodules overrides config setting" '
-	add_upstream_commit &&
+	add_submodule_commits &&
 	(
 		cd downstream &&
 		git config fetch.recurseSubmodules true &&
@@ -246,36 +335,34 @@ test_expect_success "Recursion doesn't happen when no new commits are fetched in
 '
 
 test_expect_success "Recursion stops when no new submodule commits are fetched" '
-	head1=$(git rev-parse --short HEAD) &&
 	git add submodule &&
 	git commit -m "new submodule" &&
-	head2=$(git rev-parse --short HEAD) &&
-	echo "From $pwd/." > expect.err.sub &&
-	echo "   $head1..$head2  super      -> origin/super" >>expect.err.sub &&
-	head -3 expect.err >> expect.err.sub &&
+	new_head=$(git rev-parse --short HEAD) &&
+	write_expected_super $new_head &&
+	rm expect.err.deep &&
 	(
 		cd downstream &&
 		git fetch >../actual.out 2>../actual.err
 	) &&
-	test_cmp expect.err.sub actual.err &&
+	verify_fetch_result actual.err &&
 	test_must_be_empty actual.out
 '
 
 test_expect_success "Recursion doesn't happen when new superproject commits don't change any submodules" '
-	add_upstream_commit &&
-	head1=$(git rev-parse --short HEAD) &&
+	add_submodule_commits &&
 	echo a > file &&
 	git add file &&
 	git commit -m "new file" &&
-	head2=$(git rev-parse --short HEAD) &&
-	echo "From $pwd/." > expect.err.file &&
-	echo "   $head1..$head2  super      -> origin/super" >> expect.err.file &&
+	new_head=$(git rev-parse --short HEAD) &&
+	write_expected_super $new_head &&
+	rm expect.err.sub &&
+	rm expect.err.deep &&
 	(
 		cd downstream &&
 		git fetch >../actual.out 2>../actual.err
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err.file actual.err
+	verify_fetch_result actual.err
 '
 
 test_expect_success "Recursion picks up config in submodule" '
@@ -287,14 +374,11 @@ test_expect_success "Recursion picks up config in submodule" '
 			git config fetch.recurseSubmodules true
 		)
 	) &&
-	add_upstream_commit &&
-	head1=$(git rev-parse --short HEAD) &&
+	add_submodule_commits &&
 	git add submodule &&
 	git commit -m "new submodule" &&
-	head2=$(git rev-parse --short HEAD) &&
-	echo "From $pwd/." > expect.err.sub &&
-	echo "   $head1..$head2  super      -> origin/super" >> expect.err.sub &&
-	cat expect.err >> expect.err.sub &&
+	new_head=$(git rev-parse --short HEAD) &&
+	write_expected_super $new_head &&
 	(
 		cd downstream &&
 		git fetch >../actual.out 2>../actual.err &&
@@ -303,60 +387,23 @@ test_expect_success "Recursion picks up config in submodule" '
 			git config --unset fetch.recurseSubmodules
 		)
 	) &&
-	test_cmp expect.err.sub actual.err &&
+	verify_fetch_result actual.err &&
 	test_must_be_empty actual.out
 '
 
 test_expect_success "Recursion picks up all submodules when necessary" '
-	add_upstream_commit &&
-	(
-		cd submodule &&
-		(
-			cd subdir/deepsubmodule &&
-			git fetch &&
-			git checkout -q FETCH_HEAD
-		) &&
-		head1=$(git rev-parse --short HEAD^) &&
-		git add subdir/deepsubmodule &&
-		git commit -m "new deepsubmodule" &&
-		head2=$(git rev-parse --short HEAD) &&
-		echo "Fetching submodule submodule" > ../expect.err.sub &&
-		echo "From $pwd/submodule" >> ../expect.err.sub &&
-		echo "   $head1..$head2  sub        -> origin/sub" >> ../expect.err.sub
-	) &&
-	head1=$(git rev-parse --short HEAD) &&
-	git add submodule &&
-	git commit -m "new submodule" &&
-	head2=$(git rev-parse --short HEAD) &&
-	echo "From $pwd/." > expect.err.2 &&
-	echo "   $head1..$head2  super      -> origin/super" >> expect.err.2 &&
-	cat expect.err.sub >> expect.err.2 &&
-	tail -3 expect.err >> expect.err.2 &&
+	add_submodule_commits &&
+	add_superproject_commits &&
 	(
 		cd downstream &&
 		git fetch >../actual.out 2>../actual.err
 	) &&
-	test_cmp expect.err.2 actual.err &&
+	verify_fetch_result actual.err &&
 	test_must_be_empty actual.out
 '
 
 test_expect_success "'--recurse-submodules=on-demand' doesn't recurse when no new commits are fetched in the superproject (and ignores config)" '
-	add_upstream_commit &&
-	(
-		cd submodule &&
-		(
-			cd subdir/deepsubmodule &&
-			git fetch &&
-			git checkout -q FETCH_HEAD
-		) &&
-		head1=$(git rev-parse --short HEAD^) &&
-		git add subdir/deepsubmodule &&
-		git commit -m "new deepsubmodule" &&
-		head2=$(git rev-parse --short HEAD) &&
-		echo Fetching submodule submodule > ../expect.err.sub &&
-		echo "From $pwd/submodule" >> ../expect.err.sub &&
-		echo "   $head1..$head2  sub        -> origin/sub" >> ../expect.err.sub
-	) &&
+	add_submodule_commits &&
 	(
 		cd downstream &&
 		git config fetch.recurseSubmodules true &&
@@ -368,15 +415,8 @@ test_expect_success "'--recurse-submodules=on-demand' doesn't recurse when no ne
 '
 
 test_expect_success "'--recurse-submodules=on-demand' recurses as deep as necessary (and ignores config)" '
-	head1=$(git rev-parse --short HEAD) &&
-	git add submodule &&
-	git commit -m "new submodule" &&
-	head2=$(git rev-parse --short HEAD) &&
-	tail -3 expect.err > expect.err.deepsub &&
-	echo "From $pwd/." > expect.err &&
-	echo "   $head1..$head2  super      -> origin/super" >>expect.err &&
-	cat expect.err.sub >> expect.err &&
-	cat expect.err.deepsub >> expect.err &&
+	add_submodule_commits &&
+	add_superproject_commits &&
 	(
 		cd downstream &&
 		git config fetch.recurseSubmodules false &&
@@ -392,24 +432,165 @@ test_expect_success "'--recurse-submodules=on-demand' recurses as deep as necess
 		)
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err actual.err
+	verify_fetch_result actual.err
+'
+
+# These tests verify that we can fetch submodules that aren't in the
+# index.
+#
+# First, test the simple case where the index is empty and we only fetch
+# submodules that are not in the index.
+test_expect_success 'setup downstream branch without submodules' '
+	(
+		cd downstream &&
+		git checkout --recurse-submodules -b no-submodules &&
+		git rm .gitmodules &&
+		git rm submodule &&
+		git commit -m "no submodules" &&
+		git checkout --recurse-submodules super
+	)
+'
+
+test_expect_success "'--recurse-submodules=on-demand' should fetch submodule commits if the submodule is changed but the index has no submodules" '
+	add_submodule_commits &&
+	add_superproject_commits &&
+	# Fetch the new superproject commit
+	(
+		cd downstream &&
+		git switch --recurse-submodules no-submodules &&
+		git fetch --recurse-submodules=on-demand >../actual.out 2>../actual.err
+	) &&
+	super_head=$(git rev-parse --short HEAD) &&
+	sub_head=$(git -C submodule rev-parse --short HEAD) &&
+	deep_head=$(git -C submodule/subdir/deepsubmodule rev-parse --short HEAD) &&
+
+	# assert that these are fetched from commits, not the index
+	write_expected_sub $sub_head $super_head &&
+	write_expected_deep $deep_head $sub_head &&
+
+	test_must_be_empty actual.out &&
+	verify_fetch_result actual.err
+'
+
+test_expect_success "'--recurse-submodules' should fetch submodule commits if the submodule is changed but the index has no submodules" '
+	add_submodule_commits &&
+	add_superproject_commits &&
+	# Fetch the new superproject commit
+	(
+		cd downstream &&
+		git switch --recurse-submodules no-submodules &&
+		git fetch --recurse-submodules >../actual.out 2>../actual.err
+	) &&
+	super_head=$(git rev-parse --short HEAD) &&
+	sub_head=$(git -C submodule rev-parse --short HEAD) &&
+	deep_head=$(git -C submodule/subdir/deepsubmodule rev-parse --short HEAD) &&
+
+	# assert that these are fetched from commits, not the index
+	write_expected_sub $sub_head $super_head &&
+	write_expected_deep $deep_head $sub_head &&
+
+	test_must_be_empty actual.out &&
+	verify_fetch_result actual.err
+'
+
+test_expect_success "'--recurse-submodules' should ignore changed, inactive submodules" '
+	add_submodule_commits &&
+	add_superproject_commits &&
+
+	# Fetch the new superproject commit
+	(
+		cd downstream &&
+		git switch --recurse-submodules no-submodules &&
+		git -c submodule.submodule.active=false fetch --recurse-submodules >../actual.out 2>../actual.err
+	) &&
+	test_must_be_empty actual.out &&
+	super_head=$(git rev-parse --short HEAD) &&
+	write_expected_super $super_head &&
+	# Neither should be fetched because the submodule is inactive
+	rm expect.err.sub &&
+	rm expect.err.deep &&
+	verify_fetch_result actual.err
+'
+
+# Now that we know we can fetch submodules that are not in the index,
+# test that we can fetch index and non-index submodules in the same
+# operation.
+test_expect_success 'setup downstream branch with other submodule' '
+	mkdir submodule2 &&
+	(
+		cd submodule2 &&
+		git init &&
+		echo sub2content >sub2file &&
+		git add sub2file &&
+		git commit -a -m new &&
+		git branch -M sub2
+	) &&
+	git checkout -b super-sub2-only &&
+	git submodule add "$pwd/submodule2" submodule2 &&
+	git commit -m "add sub2" &&
+	git checkout super &&
+	(
+		cd downstream &&
+		git fetch --recurse-submodules origin &&
+		git checkout super-sub2-only &&
+		# Explicitly run "git submodule update" because sub2 is new
+		# and has not been cloned.
+		git submodule update --init &&
+		git checkout --recurse-submodules super
+	)
+'
+
+test_expect_success "'--recurse-submodules' should fetch submodule commits in changed submodules and the index" '
+	test_when_finished "rm expect.err.sub2" &&
+	# Create new commit in origin/super
+	add_submodule_commits &&
+	add_superproject_commits &&
+
+	# Create new commit in origin/super-sub2-only
+	git checkout super-sub2-only &&
+	(
+		cd submodule2 &&
+		test_commit --no-tag foo
+	) &&
+	git add submodule2 &&
+	git commit -m "new submodule2" &&
+
+	git checkout super &&
+	(
+		cd downstream &&
+		git fetch --recurse-submodules >../actual.out 2>../actual.err
+	) &&
+	test_must_be_empty actual.out &&
+	sub2_head=$(git -C submodule2 rev-parse --short HEAD) &&
+	super_head=$(git rev-parse --short super) &&
+	super_sub2_only_head=$(git rev-parse --short super-sub2-only) &&
+	write_expected_sub2 $sub2_head $super_sub2_only_head &&
+
+	# write_expected_super cannot handle >1 branch. Since this is a
+	# one-off, construct expect.err.super manually.
+	cat >"$pwd/expect.err.super" <<-EOF &&
+	From $pwd/.
+	   OLD_HEAD..$super_head  super           -> origin/super
+	   OLD_HEAD..$super_sub2_only_head  super-sub2-only -> origin/super-sub2-only
+	EOF
+	verify_fetch_result actual.err
 '
 
 test_expect_success "'--recurse-submodules=on-demand' stops when no new submodule commits are found in the superproject (and ignores config)" '
-	add_upstream_commit &&
-	head1=$(git rev-parse --short HEAD) &&
+	add_submodule_commits &&
 	echo a >> file &&
 	git add file &&
 	git commit -m "new file" &&
-	head2=$(git rev-parse --short HEAD) &&
-	echo "From $pwd/." > expect.err.file &&
-	echo "   $head1..$head2  super      -> origin/super" >> expect.err.file &&
+	new_head=$(git rev-parse --short HEAD) &&
+	write_expected_super $new_head &&
+	rm expect.err.sub &&
+	rm expect.err.deep &&
 	(
 		cd downstream &&
 		git fetch --recurse-submodules=on-demand >../actual.out 2>../actual.err
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err.file actual.err
+	verify_fetch_result actual.err
 '
 
 test_expect_success "'fetch.recurseSubmodules=on-demand' overrides global config" '
@@ -417,15 +598,13 @@ test_expect_success "'fetch.recurseSubmodules=on-demand' overrides global config
 		cd downstream &&
 		git fetch --recurse-submodules
 	) &&
-	add_upstream_commit &&
+	add_submodule_commits &&
 	git config --global fetch.recurseSubmodules false &&
-	head1=$(git rev-parse --short HEAD) &&
 	git add submodule &&
 	git commit -m "new submodule" &&
-	head2=$(git rev-parse --short HEAD) &&
-	echo "From $pwd/." > expect.err.2 &&
-	echo "   $head1..$head2  super      -> origin/super" >>expect.err.2 &&
-	head -3 expect.err >> expect.err.2 &&
+	new_head=$(git rev-parse --short HEAD) &&
+	write_expected_super $new_head &&
+	rm expect.err.deep &&
 	(
 		cd downstream &&
 		git config fetch.recurseSubmodules on-demand &&
@@ -437,7 +616,7 @@ test_expect_success "'fetch.recurseSubmodules=on-demand' overrides global config
 		git config --unset fetch.recurseSubmodules
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err.2 actual.err
+	verify_fetch_result actual.err
 '
 
 test_expect_success "'submodule.<sub>.fetchRecurseSubmodules=on-demand' overrides fetch.recurseSubmodules" '
@@ -445,15 +624,13 @@ test_expect_success "'submodule.<sub>.fetchRecurseSubmodules=on-demand' override
 		cd downstream &&
 		git fetch --recurse-submodules
 	) &&
-	add_upstream_commit &&
+	add_submodule_commits &&
 	git config fetch.recurseSubmodules false &&
-	head1=$(git rev-parse --short HEAD) &&
 	git add submodule &&
 	git commit -m "new submodule" &&
-	head2=$(git rev-parse --short HEAD) &&
-	echo "From $pwd/." > expect.err.2 &&
-	echo "   $head1..$head2  super      -> origin/super" >>expect.err.2 &&
-	head -3 expect.err >> expect.err.2 &&
+	new_head=$(git rev-parse --short HEAD) &&
+	write_expected_super $new_head &&
+	rm expect.err.deep &&
 	(
 		cd downstream &&
 		git config submodule.submodule.fetchRecurseSubmodules on-demand &&
@@ -465,7 +642,7 @@ test_expect_success "'submodule.<sub>.fetchRecurseSubmodules=on-demand' override
 		git config --unset submodule.submodule.fetchRecurseSubmodules
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err.2 actual.err
+	verify_fetch_result actual.err
 '
 
 test_expect_success "don't fetch submodule when newly recorded commits are already present" '
@@ -473,18 +650,19 @@ test_expect_success "don't fetch submodule when newly recorded commits are alrea
 		cd submodule &&
 		git checkout -q HEAD^^
 	) &&
-	head1=$(git rev-parse --short HEAD) &&
 	git add submodule &&
 	git commit -m "submodule rewound" &&
-	head2=$(git rev-parse --short HEAD) &&
-	echo "From $pwd/." > expect.err &&
-	echo "   $head1..$head2  super      -> origin/super" >> expect.err &&
+	new_head=$(git rev-parse --short HEAD) &&
+	write_expected_super $new_head &&
+	rm expect.err.sub &&
+	# This file does not exist, but rm -f for readability
+	rm -f expect.err.deep &&
 	(
 		cd downstream &&
 		git fetch >../actual.out 2>../actual.err
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err actual.err &&
+	verify_fetch_result actual.err &&
 	(
 		cd submodule &&
 		git checkout -q sub
@@ -496,15 +674,13 @@ test_expect_success "'fetch.recurseSubmodules=on-demand' works also without .git
 		cd downstream &&
 		git fetch --recurse-submodules
 	) &&
-	add_upstream_commit &&
-	head1=$(git rev-parse --short HEAD) &&
+	add_submodule_commits &&
 	git add submodule &&
 	git rm .gitmodules &&
 	git commit -m "new submodule without .gitmodules" &&
-	head2=$(git rev-parse --short HEAD) &&
-	echo "From $pwd/." >expect.err.2 &&
-	echo "   $head1..$head2  super      -> origin/super" >>expect.err.2 &&
-	head -3 expect.err >>expect.err.2 &&
+	new_head=$(git rev-parse --short HEAD) &&
+	write_expected_super $new_head &&
+	rm expect.err.deep &&
 	(
 		cd downstream &&
 		rm .gitmodules &&
@@ -520,7 +696,7 @@ test_expect_success "'fetch.recurseSubmodules=on-demand' works also without .git
 		git reset --hard
 	) &&
 	test_must_be_empty actual.out &&
-	test_cmp expect.err.2 actual.err &&
+	verify_fetch_result actual.err &&
 	git checkout HEAD^ -- .gitmodules &&
 	git add .gitmodules &&
 	git commit -m "new submodule restored .gitmodules"
@@ -842,4 +1018,111 @@ test_expect_success 'recursive fetch after deinit a submodule' '
 	test_cmp expect actual
 '
 
+test_expect_success 'setup repo with upstreams that share a submodule name' '
+	mkdir same-name-1 &&
+	(
+		cd same-name-1 &&
+		git init -b main &&
+		test_commit --no-tag a
+	) &&
+	git clone same-name-1 same-name-2 &&
+	# same-name-1 and same-name-2 both add a submodule with the
+	# name "submodule"
+	(
+		cd same-name-1 &&
+		mkdir submodule &&
+		git -C submodule init -b main &&
+		test_commit -C submodule --no-tag a1 &&
+		git submodule add "$pwd/same-name-1/submodule" &&
+		git add submodule &&
+		git commit -m "super-a1"
+	) &&
+	(
+		cd same-name-2 &&
+		mkdir submodule &&
+		git -C submodule init -b main &&
+		test_commit -C submodule --no-tag a2 &&
+		git submodule add "$pwd/same-name-2/submodule" &&
+		git add submodule &&
+		git commit -m "super-a2"
+	) &&
+	git clone same-name-1 -o same-name-1 same-name-downstream &&
+	(
+		cd same-name-downstream &&
+		git remote add same-name-2 ../same-name-2 &&
+		git fetch --all &&
+		# init downstream with same-name-1
+		git submodule update --init
+	)
+'
+
+test_expect_success 'fetch --recurse-submodules updates name-conflicted, populated submodule' '
+	test_when_finished "git -C same-name-downstream checkout main" &&
+	(
+		cd same-name-1 &&
+		test_commit -C submodule --no-tag b1 &&
+		git add submodule &&
+		git commit -m "super-b1"
+	) &&
+	(
+		cd same-name-2 &&
+		test_commit -C submodule --no-tag b2 &&
+		git add submodule &&
+		git commit -m "super-b2"
+	) &&
+	(
+		cd same-name-downstream &&
+		# even though the .gitmodules is correct, we cannot
+		# fetch from same-name-2
+		git checkout same-name-2/main &&
+		git fetch --recurse-submodules same-name-1 &&
+		test_must_fail git fetch --recurse-submodules same-name-2
+	) &&
+	super_head1=$(git -C same-name-1 rev-parse HEAD) &&
+	git -C same-name-downstream cat-file -e $super_head1 &&
+
+	super_head2=$(git -C same-name-2 rev-parse HEAD) &&
+	git -C same-name-downstream cat-file -e $super_head2 &&
+
+	sub_head1=$(git -C same-name-1/submodule rev-parse HEAD) &&
+	git -C same-name-downstream/submodule cat-file -e $sub_head1 &&
+
+	sub_head2=$(git -C same-name-2/submodule rev-parse HEAD) &&
+	test_must_fail git -C same-name-downstream/submodule cat-file -e $sub_head2
+'
+
+test_expect_success 'fetch --recurse-submodules updates name-conflicted, unpopulated submodule' '
+	(
+		cd same-name-1 &&
+		test_commit -C submodule --no-tag c1 &&
+		git add submodule &&
+		git commit -m "super-c1"
+	) &&
+	(
+		cd same-name-2 &&
+		test_commit -C submodule --no-tag c2 &&
+		git add submodule &&
+		git commit -m "super-c2"
+	) &&
+	(
+		cd same-name-downstream &&
+		git checkout main &&
+		git rm .gitmodules &&
+		git rm submodule &&
+		git commit -m "no submodules" &&
+		git fetch --recurse-submodules same-name-1
+	) &&
+	head1=$(git -C same-name-1/submodule rev-parse HEAD) &&
+	head2=$(git -C same-name-2/submodule rev-parse HEAD) &&
+	(
+		cd same-name-downstream/.git/modules/submodule &&
+		# The submodule has core.worktree pointing to the "git
+		# rm"-ed directory, overwrite the invalid value. See
+		# comment in get_fetch_task_from_changed() for more
+		# information.
+		git --work-tree=. cat-file -e $head1 &&
+		test_must_fail git --work-tree=. cat-file -e $head2
+	)
+'
+
 test_done