t: use sane_unset() rather than 'unset' with broken &&-chain

These tests intentionally break the &&-chain after using 'unset' since
they don't know if 'unset' will succeed or fail and don't want a local
'unset' failure to fail the test overall. We can do better by using
sane_unset(), which can be linked into the &&-chain as usual.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t0001-init.sh

@@ -408,7 +408,7 @@ is_hidden () {
 test_expect_success MINGW '.git hidden' '
 	rm -rf newdir &&
 	(
-		unset GIT_DIR GIT_WORK_TREE
+		sane_unset GIT_DIR GIT_WORK_TREE &&
 		mkdir newdir &&
 		cd newdir &&
 		git init &&
@@ -420,7 +420,7 @@ test_expect_success MINGW '.git hidden' '
 test_expect_success MINGW 'bare git dir not hidden' '
 	rm -rf newdir &&
 	(
-		unset GIT_DIR GIT_WORK_TREE GIT_CONFIG
+		sane_unset GIT_DIR GIT_WORK_TREE GIT_CONFIG &&
 		mkdir newdir &&
 		cd newdir &&
 		git --bare init

t/t1300-config.sh

@@ -888,7 +888,7 @@ EOF
 
 test_expect_success !MINGW 'get --path copes with unset $HOME' '
 	(
-		unset HOME;
+		sane_unset HOME &&
 		test_must_fail git config --get --path path.home \
 			>result 2>msg &&
 		git config --get --path path.normal >>result &&