@@ -0,0 +1,166 @@
+#!/bin/sh
+
+test_description='submodule with multiple worktrees'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	git config extensions.worktreeConfig true &&
+	>t &&
+	git add t &&
+	git commit -m initial &&
+	git branch initial
+'
+
+test_expect_success 'setup - repository in init subdirectory' '
+	mkdir init &&
+	(
+		cd init &&
+		git init &&
+		git config extensions.worktreeConfig true &&
+		echo a >a &&
+		git add a &&
+		git commit -m "submodule commit 1" &&
+		git tag -a -m "rev-1" rev-1
+	)
+'
+
+test_expect_success 'setup - commit with gitlink' '
+	echo a >a &&
+	echo z >z &&
+	git add a init z &&
+	git commit -m "super commit 1"
+'
+
+test_expect_success 'setup - hide init subdirectory' '
+	mv init .subrepo
+'
+
+test_expect_success 'setup - repository to add submodules to' '
+	git init addtest &&
+	git -C addtest config extensions.worktreeConfig true &&
+	git init addtest-ignore &&
+	git -C addtest-ignore config extensions.worktreeConfig true
+'
+
+# The 'submodule add' tests need some repository to add as a submodule.
+# The trash directory is a good one as any. We need to canonicalize
+# the name, though, as some tests compare it to the absolute path git
+# generates, which will expand symbolic links.
+submodurl=$(pwd -P)
+
+listbranches() {
+	git for-each-ref --format='%(refname)' 'refs/heads/*'
+}
+
+inspect() {
+	dir=$1 &&
+	dotdot="${2:-..}" &&
+
+	(
+		cd "$dir" &&
+		listbranches >"$dotdot/heads" &&
+		{ git symbolic-ref HEAD || :; } >"$dotdot/head" &&
+		git rev-parse HEAD >"$dotdot/head-sha1" &&
+		git update-index --refresh &&
+		git diff-files --exit-code &&
+		git clean -n -d -x >"$dotdot/untracked"
+	)
+}
+
+test_expect_success 'submodule add' '
+	echo "refs/heads/master" >expect &&
+	>empty &&
+
+	(
+		cd addtest &&
+		git submodule add -q "$submodurl" submod >actual &&
+		test_must_be_empty actual &&
+		echo "gitdir: ../.git/modules/submod" >expect &&
+		test_cmp expect submod/.git &&
+		(
+			cd submod &&
+			git config core.worktree >actual &&
+			echo "../../../submod" >expect &&
+			test_cmp expect actual &&
+			rm -f actual expect
+		) &&
+		git submodule init
+	) &&
+
+	rm -f heads head untracked &&
+	inspect addtest/submod ../.. &&
+	test_cmp expect heads &&
+	test_cmp expect head &&
+	test_cmp empty untracked
+'
+
+test_expect_success 'submodule.* in supermodule is per-worktree' '
+	(
+		cd addtest &&
+		git config -f .git/config.worktree submodule.submod.url >actual &&
+		echo "$submodurl" >expect &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'turn submodule to multiworktree' '
+	(
+		cd addtest/.git/modules/submod &&
+		CORE_WT="$(git config core.worktree)" &&
+		git config -f config.worktree core.worktree "$CORE_WT" &&
+		git config --unset core.worktree &&
+		git config extensions.worktreeConfig true &&
+		git config core.worktree >actual &&
+		echo "$CORE_WT" >expect &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'new worktree in submodule' '
+	(
+		cd addtest/submod &&
+		git worktree add submod-elsewhere &&
+		cd submod-elsewhere &&
+		test_must_fail git config core.worktree
+	)
+'
+
+test_expect_success 'new worktree in supermodule' '
+	(
+		cd addtest &&
+		git commit -m initial &&
+		git worktree add super-elsewhere &&
+		cd super-elsewhere &&
+		test_must_fail git config submodule.submode
+	)
+'
+
+test_expect_success 'submodule add in the second worktree' '
+	(
+		cd addtest/super-elsewhere &&
+		git submodule add -q "$submodurl" submod2 >actual &&
+		test_must_be_empty actual &&
+		echo "gitdir: ../../.git/worktrees/super-elsewhere/modules/submod2" >expect &&
+		test_cmp expect submod2/.git &&
+		(
+			cd submod2 &&
+			git config core.worktree >actual &&
+			echo "../../../../../super-elsewhere/submod2" >expect &&
+			test_cmp expect actual &&
+			rm -f actual expect
+		) &&
+		git submodule init
+	)
+'
+
+test_expect_success 'submodule.* in supermodule is per-worktree' '
+	(
+		cd addtest/super-elsewhere &&
+		git config -f ../.git/worktrees/super-elsewhere/config.worktree submodule.submod2.url >actual &&
+		echo "$submodurl" >expect &&
+		test_cmp expect actual
+	)
+'
+
+test_done