subtree: fix argument handling in check_parents

check_parents was taking all of its arguments as a single string,
and erroneously passing them to cache_miss as a single string.
cache_miss would then fail, and the spurious cache misses it produced
would hurt performance.

For consistency, take multiple arguments in check_parents,
and pass all of them to cache_miss separately.

Signed-off-by: James Limbouris <james@digitalmatter.com>

contrib/subtree/git-subtree.sh

@@ -296,10 +296,9 @@ cache_miss () {
 	done
 }
 
-# Usage: check_parents PARENTS_EXPR
+# Usage: check_parents [REVS...]
 check_parents () {
-	assert test $# = 1
-	missed=$(cache_miss "$1") || exit $?
+	missed=$(cache_miss "$@") || exit $?
 	local indent=$(($indent + 1))
 	for miss in $missed
 	do
@@ -753,7 +752,7 @@ process_split_commit () {
 	fi
 	createcount=$(($createcount + 1))
 	debug "parents: $parents"
-	check_parents "$parents"
+	check_parents $parents
 	newparents=$(cache_get $parents) || exit $?
 	debug "newparents: $newparents"