Make the config file path a flag until we get rid of all the flags

cmd/bb_portal/main.go

@@ -12,8 +12,6 @@ import (
 	_ "github.com/mattn/go-sqlite3"
 	build "google.golang.org/genproto/googleapis/devtools/build/v1"
 	go_grpc "google.golang.org/grpc"
-	"google.golang.org/grpc/codes"
-	"google.golang.org/grpc/status"
 
 	"github.com/buildbarn/bb-portal/ent/gen/ent"
 	"github.com/buildbarn/bb-portal/ent/gen/ent/migrate"
@@ -34,6 +32,7 @@ const (
 )
 
 var (
+	configFile               = flag.String("config-file", "bb_portal.jsonnet", "bb_portal config file")
 	dsDriver                 = flag.String("datasource-driver", "sqlite3", "Data source driver to use")
 	dsURL                    = flag.String("datasource-url", "file:buildportal.db?_journal=WAL&_fk=1", "Data source URL for the DB")
 	bepFolder                = flag.String("bep-folder", "./bep-files/", "Folder to watch for new BEP files")
@@ -47,12 +46,8 @@ func main() {
 	program.RunMain(func(ctx context.Context, siblingsGroup, dependenciesGroup program.Group) error {
 		flag.Parse()
 
-		if len(os.Args) != 2 {
-			return status.Error(codes.InvalidArgument, "Usage: bb_portal bb_portal.jsonnet")
-		}
-
 		var configuration bb_portal.ApplicationConfiguration
-		if err := util.UnmarshalConfigurationFromFile(os.Args[1], &configuration); err != nil {
+		if err := util.UnmarshalConfigurationFromFile(*configFile, &configuration); err != nil {
 			return util.StatusWrapf(err, "Failed to read configuration from %s", os.Args[1])
 		}