fast-import.c: use a ref transaction when dumping tags

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

fast-import.c

@@ -1735,15 +1735,32 @@ static void dump_tags(void)
 {
 	static const char *msg = "fast-import";
 	struct tag *t;
-	struct ref_lock *lock;
-	char ref_name[PATH_MAX];
+	struct strbuf ref_name = STRBUF_INIT;
+	struct strbuf err = STRBUF_INIT;
+	struct ref_transaction *transaction;
 
+	transaction = ref_transaction_begin(&err);
+	if (!transaction) {
+		failure |= error("%s", err.buf);
+		goto cleanup;
+	}
 	for (t = first_tag; t; t = t->next_tag) {
-		sprintf(ref_name, "tags/%s", t->name);
-		lock = lock_ref_sha1(ref_name, NULL);
-		if (!lock || write_ref_sha1(lock, t->sha1, msg) < 0)
-			failure |= error("Unable to update %s", ref_name);
+		strbuf_reset(&ref_name);
+		strbuf_addf(&ref_name, "refs/tags/%s", t->name);
+
+		if (ref_transaction_update(transaction, ref_name.buf, t->sha1,
+					   NULL, 0, 0, &err)) {
+			failure |= error("%s", err.buf);
+			goto cleanup;
+		}
 	}
+	if (ref_transaction_commit(transaction, msg, &err))
+		failure |= error("%s", err.buf);
+
+ cleanup:
+	ref_transaction_free(transaction);
+	strbuf_release(&ref_name);
+	strbuf_release(&err);
 }
 
 static void dump_marks_helper(FILE *f,