Merge branch 'jc/checkout-from-tree-keep-local-changes'

* jc/checkout-from-tree-keep-local-changes:
  checkout $tree $path: do not clobber local changes in $path not in $tree

t/t2022-checkout-paths.sh

@@ -0,0 +1,42 @@
+#!/bin/sh
+
+test_description='checkout $tree -- $paths'
+. ./test-lib.sh
+
+test_expect_success setup '
+	mkdir dir &&
+	>dir/master &&
+	echo common >dir/common &&
+	git add dir/master dir/common &&
+	test_tick && git commit -m "master has dir/master" &&
+	git checkout -b next &&
+	git mv dir/master dir/next0 &&
+	echo next >dir/next1 &&
+	git add dir &&
+	test_tick && git commit -m "next has dir/next but not dir/master"
+'
+
+test_expect_success 'checking out paths out of a tree does not clobber unrelated paths' '
+	git checkout next &&
+	git reset --hard &&
+	rm dir/next0 &&
+	cat dir/common >expect.common &&
+	echo modified >expect.next1 &&
+	cat expect.next1 >dir/next1 &&
+	echo untracked >expect.next2 &&
+	cat expect.next2 >dir/next2 &&
+
+	git checkout master dir &&
+
+	test_cmp expect.common dir/common &&
+	test_path_is_file dir/master &&
+	git diff --exit-code master dir/master &&
+
+	test_path_is_missing dir/next0 &&
+	test_cmp expect.next1 dir/next1 &&
+	test_path_is_file dir/next2 &&
+	test_must_fail git ls-files --error-unmatch dir/next2 &&
+	test_cmp expect.next2 dir/next2
+'
+
+test_done