refs: enable sign compare warnings check

After fixing the tricky compare warning introduced by calling
"string_list_find_insert_index", there are only two loop iterator type
mismatches. Fix them to enable compare warnings check.

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

Author: shejialuo

refs.c

@@ -3,7 +3,6 @@
  */
 
 #define USE_THE_REPOSITORY_VARIABLE
-#define DISABLE_SIGN_COMPARE_WARNINGS
 
 #include "git-compat-util.h"
 #include "advice.h"
@@ -2381,7 +2380,7 @@ static int run_transaction_hook(struct ref_transaction *transaction,
 	struct child_process proc = CHILD_PROCESS_INIT;
 	struct strbuf buf = STRBUF_INIT;
 	const char *hook;
-	int ret = 0, i;
+	int ret = 0;
 
 	hook = find_hook(transaction->ref_store->repo, "reference-transaction");
 	if (!hook)
@@ -2398,7 +2397,7 @@ static int run_transaction_hook(struct ref_transaction *transaction,
 
 	sigchain_push(SIGPIPE, SIG_IGN);
 
-	for (i = 0; i < transaction->nr; i++) {
+	for (size_t i = 0; i < transaction->nr; i++) {
 		struct ref_update *update = transaction->updates[i];
 
 		if (update->flags & REF_LOG_ONLY)
@@ -2791,9 +2790,7 @@ void ref_transaction_for_each_queued_update(struct ref_transaction *transaction,
 					    ref_transaction_for_each_queued_update_fn cb,
 					    void *cb_data)
 {
-	int i;
-
-	for (i = 0; i < transaction->nr; i++) {
+	for (size_t i = 0; i < transaction->nr; i++) {
 		struct ref_update *update = transaction->updates[i];
 
 		cb(update->refname,