t1092: test merge conflicts outside cone

Conflicts can occur outside of the sparse-checkout definition, and in
that case users might try to resolve the conflicts in several ways.
Document a few of these ways in a test. Make it clear that this behavior
is not necessarily the optimal flow, since users can become confused
when Git deletes these files from the worktree in later commands.

Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

t/t1092-sparse-checkout-compatibility.sh

@@ -114,6 +114,16 @@ test_expect_success 'setup' '
 		git add . &&
 		git commit -m "file to dir" &&
 
+		for side in left right
+		do
+			git checkout -b merge-$side base &&
+			echo $side >>deep/deeper2/a &&
+			echo $side >>folder1/a &&
+			echo $side >>folder2/a &&
+			git add . &&
+			git commit -m "$side" || return 1
+		done &&
+
 		git checkout -b deepest base &&
 		echo "updated deepest" >deep/deeper1/deepest/a &&
 		git commit -a -m "update deepest" &&
@@ -482,6 +492,39 @@ test_expect_success 'merge' '
 	test_all_match git rev-parse HEAD^{tree}
 '
 
+# NEEDSWORK: This test is documenting current behavior, but that
+# behavior can be confusing to users so there is desire to change it.
+# Right now, users might be using this flow to work through conflicts,
+# so any solution should present advice to users who try this sequence
+# of commands to follow whatever new method we create.
+test_expect_success 'merge with conflict outside cone' '
+	init_repos &&
+
+	test_all_match git checkout -b merge-tip merge-left &&
+	test_all_match git status --porcelain=v2 &&
+	test_all_match test_must_fail git merge -m merge merge-right &&
+	test_all_match git status --porcelain=v2 &&
+
+	# Resolve the conflict in different ways:
+	# 1. Revert to the base
+	test_all_match git checkout base -- deep/deeper2/a &&
+	test_all_match git status --porcelain=v2 &&
+
+	# 2. Add the file with conflict markers
+	test_all_match git add folder1/a &&
+	test_all_match git status --porcelain=v2 &&
+
+	# 3. Rename the file to another sparse filename and
+	#    accept conflict markers as resolved content.
+	run_on_all mv folder2/a folder2/z &&
+	test_all_match git add folder2 &&
+	test_all_match git status --porcelain=v2 &&
+
+	test_all_match git merge --continue &&
+	test_all_match git status --porcelain=v2 &&
+	test_all_match git rev-parse HEAD^{tree}
+'
+
 test_expect_success 'merge with outside renames' '
 	init_repos &&