t7300: fix broken && chains

While we are here, remove some boilerplate by using test_commit.

Signed-off-by: Erik Elfström <erik.elfstrom@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: elfstrom

t/t7300-clean.sh

@@ -404,9 +404,7 @@ test_expect_success 'nested git work tree' '
 	(
 		cd foo &&
 		git init &&
-		>hello.world
-		git add . &&
-		git commit -a -m nested
+		test_commit nested hello.world
 	) &&
 	(
 		cd bar &&
@@ -415,9 +413,7 @@ test_expect_success 'nested git work tree' '
 	(
 		cd baz/boo &&
 		git init &&
-		>deeper.world
-		git add . &&
-		git commit -a -m deeply.nested
+		test_commit deeply.nested deeper.world
 	) &&
 	git clean -f -d &&
 	test -f foo/.git/index &&
@@ -433,9 +429,7 @@ test_expect_success 'force removal of nested git work tree' '
 	(
 		cd foo &&
 		git init &&
-		>hello.world
-		git add . &&
-		git commit -a -m nested
+		test_commit nested hello.world
 	) &&
 	(
 		cd bar &&
@@ -444,9 +438,7 @@ test_expect_success 'force removal of nested git work tree' '
 	(
 		cd baz/boo &&
 		git init &&
-		>deeper.world
-		git add . &&
-		git commit -a -m deeply.nested
+		test_commit deeply.nested deeper.world
 	) &&
 	git clean -f -f -d &&
 	! test -d foo &&