t0033: add tests for safe.directory

It is difficult to change the ownership on a directory in our test
suite, so insert a new GIT_TEST_ASSUME_DIFFERENT_OWNER environment
variable to trick Git into thinking we are in a differently-owned
directory. This allows us to test that the config is parsed correctly.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

setup.c

@@ -1053,7 +1053,8 @@ static int ensure_valid_ownership(const char *path)
 {
 	struct safe_directory_data data = { .path = path };
 
-	if (is_path_owned_by_current_user(path))
+	if (!git_env_bool("GIT_TEST_ASSUME_DIFFERENT_OWNER", 0) &&
+	    is_path_owned_by_current_user(path))
 		return 1;
 
 	read_very_early_config(safe_directory_cb, &data);

t/t0033-safe-directory.sh

@@ -0,0 +1,34 @@
+#!/bin/sh
+
+test_description='verify safe.directory checks'
+
+. ./test-lib.sh
+
+GIT_TEST_ASSUME_DIFFERENT_OWNER=1
+export GIT_TEST_ASSUME_DIFFERENT_OWNER
+
+expect_rejected_dir () {
+	test_must_fail git status 2>err &&
+	grep "safe.directory" err
+}
+
+test_expect_success 'safe.directory is not set' '
+	expect_rejected_dir
+'
+
+test_expect_success 'safe.directory does not match' '
+	git config --global safe.directory bogus &&
+	expect_rejected_dir
+'
+
+test_expect_success 'safe.directory matches' '
+	git config --global --add safe.directory "$(pwd)" &&
+	git status
+'
+
+test_expect_success 'safe.directory matches, but is reset' '
+	git config --global --add safe.directory "" &&
+	expect_rejected_dir
+'
+
+test_done