Prevent checkout_tree when conflicts exist, clear NAME on checkout tree

Prevent checkout tree when unresolved changes exist (unless FORCE flag
is specified).  Clear NAME table when checking out, to avoid
checkout_conflicts from attempting to manipulate it.  Ensure that NAME
is also cleared at reset.

tests-clar/checkout/tree.c

@@ -696,3 +696,47 @@ void test_checkout_tree__extremely_long_file_name(void)
 	cl_git_pass(git_checkout_tree(g_repo, g_object, &g_opts));
 	cl_assert(!git_path_exists(path));
 }
+
+static void create_conflict(void)
+{
+	git_index *index;
+	git_index_entry entry;
+
+	cl_git_pass(git_repository_index(&index, g_repo));
+
+	memset(&entry, 0x0, sizeof(git_index_entry));
+	entry.mode = 0100644;
+	entry.flags = 1 << GIT_IDXENTRY_STAGESHIFT;
+	git_oid_fromstr(&entry.oid, "d427e0b2e138501a3d15cc376077a3631e15bd46");
+	entry.path = "conflicts.txt";
+	cl_git_pass(git_index_add(index, &entry));
+
+	entry.flags = 2 << GIT_IDXENTRY_STAGESHIFT;
+	git_oid_fromstr(&entry.oid, "ee3fa1b8c00aff7fe02065fdb50864bb0d932ccf");
+	cl_git_pass(git_index_add(index, &entry));
+
+	entry.flags = 3 << GIT_IDXENTRY_STAGESHIFT;
+	git_oid_fromstr(&entry.oid, "2bd0a343aeef7a2cf0d158478966a6e587ff3863");
+	cl_git_pass(git_index_add(index, &entry));
+
+	git_index_write(index);
+	git_index_free(index);
+}
+
+void test_checkout_tree__fails_when_conflicts_exist_in_index(void)
+{
+	git_checkout_opts opts = GIT_CHECKOUT_OPTS_INIT;
+	git_oid oid;
+	git_object *obj = NULL;
+
+	opts.checkout_strategy = GIT_CHECKOUT_SAFE;
+
+	cl_git_pass(git_reference_name_to_id(&oid, g_repo, "HEAD"));
+	cl_git_pass(git_object_lookup(&obj, g_repo, &oid, GIT_OBJ_ANY));
+
+	create_conflict();
+
+	cl_git_fail(git_checkout_tree(g_repo, obj, &opts));
+
+	git_object_free(obj);
+}

tests-clar/index/names.c

@@ -80,5 +80,69 @@ void test_index_names__roundtrip(void)
 	cl_assert(strcmp(conflict_name->ancestor, "ancestor3") == 0);
 	cl_assert(conflict_name->ours == NULL);
 	cl_assert(strcmp(conflict_name->theirs, "theirs3") == 0);
+}
+
+void test_index_names__cleaned_on_reset_hard(void)
+{
+	git_object *target;
+
+	retrieve_target_from_oid(&target, repo, "3a34580a35add43a4cf361e8e9a30060a905c876");
+
+	test_index_names__add();
+	cl_git_pass(git_reset(repo, target, GIT_RESET_HARD));
+	cl_assert(git_index_name_entrycount(repo_index) == 0);
+
+	git_object_free(target);
+}
+
+void test_index_names__cleaned_on_reset_mixed(void)
+{
+	git_object *target;
+
+	retrieve_target_from_oid(&target, repo, "3a34580a35add43a4cf361e8e9a30060a905c876");
+
+	test_index_names__add();
+	cl_git_pass(git_reset(repo, target, GIT_RESET_MIXED));
+	cl_assert(git_index_name_entrycount(repo_index) == 0);
+
+	git_object_free(target);
+}
+
+void test_index_names__cleaned_on_checkout_tree(void)
+{
+	git_oid oid;
+	git_object *obj;
+	git_checkout_opts opts = GIT_CHECKOUT_OPTS_INIT;
+
+	opts.checkout_strategy = GIT_CHECKOUT_SAFE | GIT_CHECKOUT_UPDATE_ONLY;
+
+	test_index_names__add();
+	git_reference_name_to_id(&oid, repo, "refs/heads/master");
+	git_object_lookup(&obj, repo, &oid, GIT_OBJ_ANY);
+	git_checkout_tree(repo, obj, &opts);
+	cl_assert(git_index_name_entrycount(repo_index) == 0);
+
+	git_object_free(obj);
+}
+
+void test_index_names__cleaned_on_checkout_head(void)
+{
+	git_checkout_opts opts = GIT_CHECKOUT_OPTS_INIT;
+
+	opts.checkout_strategy = GIT_CHECKOUT_SAFE | GIT_CHECKOUT_UPDATE_ONLY;
+
+	test_index_names__add();
+	git_checkout_head(repo, &opts);
+	cl_assert(git_index_name_entrycount(repo_index) == 0);
+}
+
+void test_index_names__retained_on_checkout_index(void)
+{
+	git_checkout_opts opts = GIT_CHECKOUT_OPTS_INIT;
+
+	opts.checkout_strategy = GIT_CHECKOUT_SAFE | GIT_CHECKOUT_UPDATE_ONLY;
 
+	test_index_names__add();
+	git_checkout_index(repo, repo_index, &opts);
+	cl_assert(git_index_name_entrycount(repo_index) > 0);
 }