for-each-ref: clean up code

In 'grab_single_ref()' remove the extra count variable 'cnt' and
use the variable 'grab_cnt' of structure 'grab_ref_cbdata' directly
instead.

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Reviewed-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/for-each-ref.c

@@ -897,7 +897,6 @@ static int grab_single_ref(const char *refname, const struct object_id *oid,
 {
 	struct grab_ref_cbdata *cb = cb_data;
 	struct refinfo *ref;
-	int cnt;
 
 	if (flag & REF_BAD_NAME) {
 		  warning("ignoring ref with broken name %s", refname);
@@ -914,10 +913,8 @@ static int grab_single_ref(const char *refname, const struct object_id *oid,
 	 */
 	ref = new_refinfo(refname, oid->hash, flag);
 
-	cnt = cb->grab_cnt;
-	REALLOC_ARRAY(cb->grab_array, cnt + 1);
-	cb->grab_array[cnt++] = ref;
-	cb->grab_cnt = cnt;
+	REALLOC_ARRAY(cb->grab_array, cb->grab_cnt + 1);
+	cb->grab_array[cb->grab_cnt++] = ref;
 	return 0;
 }