t9124: clean up chdir usage

Spawn subshells when running things in subdirectories instead of
chdir-ing to the path of an undefined variable, which is
confusing.

Signed-off-by: Eric Wong <normalperson@yhbt.net>

t/t9124-git-svn-dcommit-auto-props.sh

@@ -29,13 +29,11 @@ test_expect_success 'initialize git-svn' '
 '
 
 test_expect_success 'enable auto-props config' '
-	cd "$gittestrepo" &&
 	mkdir user &&
 	generate_auto_props yes >user/config
 '
 
 test_expect_success 'add files matching auto-props' '
-	cd "$gittestrepo" &&
 	echo "#!$SHELL_PATH" >exec1.sh &&
 	chmod +x exec1.sh &&
 	echo "hello" >hello.txt &&
@@ -46,12 +44,10 @@ test_expect_success 'add files matching auto-props' '
 '
 
 test_expect_success 'disable auto-props config' '
-	cd "$gittestrepo" &&
 	generate_auto_props no >user/config
 '
 
 test_expect_success 'add files matching disabled auto-props' '
-	cd "$gittestrepo" &&
 	echo "#$SHELL_PATH" >exec2.sh &&
 	chmod +x exec2.sh &&
 	echo "world" >world.txt &&
@@ -62,6 +58,7 @@ test_expect_success 'add files matching disabled auto-props' '
 '
 
 test_expect_success 'check resulting svn repository' '
+(
 	mkdir work &&
 	cd work &&
 	svn co "$svnrepo" &&
@@ -81,6 +78,7 @@ test_expect_success 'check resulting svn repository' '
 	test "x$(svn propget svn:mime-type world.txt)" = "x" &&
 	test "x$(svn propget svn:eol-style world.txt)" = "x" &&
 	test "x$(svn propget svn:mime-type zot)" = "x"
+)
 '
 
 test_done