wallet: fix migration of existing invoices's id variable.

Rusty can't type.  Rusty can't test.  Bad Rusty.  Bad.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/test_invoices.py

@@ -913,7 +913,6 @@ def test_listinvoices_index(node_factory, executor):
         assert only_one(l2.rpc.listinvoices(index='updated', start=i, limit=1)['invoices'])['label'] == str(70 + 1 - i)
 
 
-@pytest.mark.xfail(strict=True)
 @unittest.skipIf(TEST_NETWORK != 'regtest', "The DB migration is network specific due to the chain var.")
 def test_invoices_wait_db_migration(node_factory, bitcoind):
     """Canned db is from v23.02.2's test_invoice_routeboost_private l2"""

wallet/db.c

@@ -70,6 +70,9 @@ static void migrate_normalize_invstr(struct lightningd *ld,
 static void migrate_initialize_wait_indexes(struct lightningd *ld,
 					    struct db *db);
 
+static void migrate_invoice_created_index_var(struct lightningd *ld,
+					      struct db *db);
+
 /* Do not reorder or remove elements from this array, it is used to
  * migrate existing databases from a previous state, based on the
  * string indices */
@@ -966,6 +969,7 @@ static struct migration dbmigrations[] = {
     {SQL("ALTER TABLE invoices ADD updated_index BIGINT DEFAULT 0"), NULL},
     {SQL("CREATE INDEX invoice_update_idx ON invoices (updated_index)"), NULL},
     {NULL, migrate_datastore_commando_runes},
+    {NULL, migrate_invoice_created_index_var},
 };
 
 /**
@@ -1672,6 +1676,18 @@ static void migrate_initialize_wait_indexes(struct lightningd *ld,
 	tal_free(stmt);
 }
 
+static void migrate_invoice_created_index_var(struct lightningd *ld, struct db *db)
+{
+	struct db_stmt *stmt;
+
+	/* Prior migration had a typo! */
+	stmt = db_prepare_v2(db, SQL("UPDATE vars"
+				     " SET name = 'last_invoices_created_index'"
+				     " WHERE name = 'last_invoice_created_index'"));
+	db_exec_prepared_v2(stmt);
+	tal_free(stmt);
+}
+
 static void complain_unfixed(struct lightningd *ld,
 			     enum channel_state state,
 			     u64 id,