t: local VAR="VAL" (quote command substitution)

Future-proof test scripts that do

	local VAR=VAL

without quoting VAL (which is OK in POSIX but broken in some shells)
that is a $(command substitution).

Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/test-lib-functions.sh

@@ -1840,7 +1840,7 @@ test_subcommand () {
 		shift
 	fi
 
-	local expr=$(printf '"%s",' "$@")
+	local expr="$(printf '"%s",' "$@")"
 	expr="${expr%,}"
 
 	if test -n "$negate"