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

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

builtin/checkout.c

@@ -71,7 +71,7 @@ static int update_some(const unsigned char *sha1, const char *base, int baselen,
 	hashcpy(ce->sha1, sha1);
 	memcpy(ce->name, base, baselen);
 	memcpy(ce->name + baselen, pathname, len - baselen);
-	ce->ce_flags = create_ce_flags(len, 0);
+	ce->ce_flags = create_ce_flags(len, 0) | CE_UPDATE;
 	ce->ce_mode = create_ce_mode(mode);
 	add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
 	return 0;
@@ -228,6 +228,8 @@ static int checkout_paths(struct tree *source_tree, const char **pathspec,
 
 	for (pos = 0; pos < active_nr; pos++) {
 		struct cache_entry *ce = active_cache[pos];
+		if (source_tree && !(ce->ce_flags & CE_UPDATE))
+			continue;
 		match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, ps_matched);
 	}
 
@@ -266,6 +268,8 @@ static int checkout_paths(struct tree *source_tree, const char **pathspec,
 	state.refresh_cache = 1;
 	for (pos = 0; pos < active_nr; pos++) {
 		struct cache_entry *ce = active_cache[pos];
+		if (source_tree && !(ce->ce_flags & CE_UPDATE))
+			continue;
 		if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
 			if (!ce_stage(ce)) {
 				errs |= checkout_entry(ce, &state, NULL);

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