refactor: use flags instead of positionals, reorganize cli init

cobble.go

@@ -23,12 +23,13 @@ func SetupDatabaseConnection(cmd *cobra.Command, args []string) {
 	cmd.SetContext(context.WithValue(cmd.Context(), "db", db))
 }
 
-var cli = &cobra.Command{
+func NewCli() *cobra.Command {
+	cli := &cobra.Command{
 		Use:   "cobble",
 		Short: "Cobble is a simple SQL migration utility.",
-}
+	}
 
-var up = &cobra.Command{
+	up := &cobra.Command{
 		Use:    "up",
 		Short:  "Applies migrations",
 		PreRun: SetupDatabaseConnection,
@@ -44,14 +45,14 @@ var up = &cobra.Command{
 				}
 			}
 		},
-}
+	}
 
-var inspect = &cobra.Command{
+	inspect := &cobra.Command{
 		Use:   "inspect",
 		Short: "Prints the nth migration in the history",
 		Run: func(cmd *cobra.Command, args []string) {
-		migrationRoot := args[0]
-		migrationIndex, _ := strconv.Atoi(args[1])
+			migrationRoot, _ := cmd.Flags().GetString("root")
+			migrationIndex, _ := cmd.Flags().GetInt("index")
 
 			migrationGraph, _ := NewMigrationGraphFromDirectory(migrationRoot)
 			migrationHistory, _ := migrationGraph.GetLinearHistory()
@@ -59,13 +60,20 @@ var inspect = &cobra.Command{
 			sql, _ := migration.Sql()
 			fmt.Printf("%s:\n%s", migration.Name, sql)
 		},
-}
-
-func main() {
+	}
 	cli.AddCommand(up)
 	cli.AddCommand(inspect)
 
-	if err := cli.Execute(); err != nil {
+	cli.PersistentFlags().StringP("root", "r", "./migrations", "Root directory where migration files live.")
+	inspect.PersistentFlags().IntP("index", "i", 0, "Zero-based index of the migration to target.")
+
+	inspect.MarkFlagRequired("index")
+
+	return cli
+}
+
+func main() {
+	if err := NewCli().Execute(); err != nil {
 		log.Fatal(err)
 		os.Exit(1)
 	}