diff --git a/refs.c b/refs.c
index 5dc2473fbb..7c4eeb1c99 100644
--- a/refs.c
+++ b/refs.c
@@ -766,13 +766,33 @@ void ref_transaction_free(struct ref_transaction *transaction)
 	free(transaction);
 }
 
-static struct ref_update *add_update(struct ref_transaction *transaction,
-				     const char *refname)
+struct ref_update *ref_transaction_add_update(
+		struct ref_transaction *transaction,
+		const char *refname, unsigned int flags,
+		const unsigned char *new_sha1,
+		const unsigned char *old_sha1,
+		const char *msg)
 {
 	struct ref_update *update;
+
+	if (transaction->state != REF_TRANSACTION_OPEN)
+		die("BUG: update called for transaction that is not open");
+
+	if ((flags & REF_ISPRUNING) && !(flags & REF_NODEREF))
+		die("BUG: REF_ISPRUNING set without REF_NODEREF");
+
 	FLEX_ALLOC_STR(update, refname, refname);
 	ALLOC_GROW(transaction->updates, transaction->nr + 1, transaction->alloc);
 	transaction->updates[transaction->nr++] = update;
+
+	update->flags = flags;
+
+	if (flags & REF_HAVE_NEW)
+		hashcpy(update->new_sha1, new_sha1);
+	if (flags & REF_HAVE_OLD)
+		hashcpy(update->old_sha1, old_sha1);
+	if (msg)
+		update->msg = xstrdup(msg);
 	return update;
 }
 
@@ -783,16 +803,8 @@ int ref_transaction_update(struct ref_transaction *transaction,
 			   unsigned int flags, const char *msg,
 			   struct strbuf *err)
 {
-	struct ref_update *update;
-
 	assert(err);
 
-	if (transaction->state != REF_TRANSACTION_OPEN)
-		die("BUG: update called for transaction that is not open");
-
-	if ((flags & REF_ISPRUNING) && !(flags & REF_NODEREF))
-		die("BUG: REF_ISPRUNING set without REF_NODEREF");
-
 	if (new_sha1 && !is_null_sha1(new_sha1) &&
 	    check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
 		strbuf_addf(err, "refusing to update ref with bad name '%s'",
@@ -800,18 +812,10 @@ int ref_transaction_update(struct ref_transaction *transaction,
 		return -1;
 	}
 
-	update = add_update(transaction, refname);
-	if (new_sha1) {
-		hashcpy(update->new_sha1, new_sha1);
-		flags |= REF_HAVE_NEW;
-	}
-	if (old_sha1) {
-		hashcpy(update->old_sha1, old_sha1);
-		flags |= REF_HAVE_OLD;
-	}
-	update->flags = flags;
-	if (msg)
-		update->msg = xstrdup(msg);
+	flags |= (new_sha1 ? REF_HAVE_NEW : 0) | (old_sha1 ? REF_HAVE_OLD : 0);
+
+	ref_transaction_add_update(transaction, refname, flags,
+				   new_sha1, old_sha1, msg);
 	return 0;
 }
 
diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index 9686e60942..babdf2769f 100644
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h
@@ -157,6 +157,20 @@ struct ref_update {
 	const char refname[FLEX_ARRAY];
 };
 
+/*
+ * Add a ref_update with the specified properties to transaction, and
+ * return a pointer to the new object. This function does not verify
+ * that refname is well-formed. new_sha1 and old_sha1 are only
+ * dereferenced if the REF_HAVE_NEW and REF_HAVE_OLD bits,
+ * respectively, are set in flags.
+ */
+struct ref_update *ref_transaction_add_update(
+		struct ref_transaction *transaction,
+		const char *refname, unsigned int flags,
+		const unsigned char *new_sha1,
+		const unsigned char *old_sha1,
+		const char *msg);
+
 /*
  * Transaction states.
  * OPEN:   The transaction is in a valid state and can accept new updates.