Back then I forgot it is not C, just compare with full strings in switch.

cmd/mccl/main.go

@@ -131,102 +131,50 @@ func parseArguments(args []string) (parsed arguments, err error) {
 	parsed.Username = "Anonymous"
 	parsed.Directory = "."
 	parsed.Uuid = "00000000-0000-0000-0000-000000000000"
+
 	for i := 0; i < len(args); i++ {
-		if len(args[i]) > 2 && args[i][0] == '-' && args[i][1] == '-' {
+		switch args[i] {
-			switch args[i][2:] {
+		case "-v":
-			case "version":
+			fallthrough
+		case "--version":
 			parsed.ShowVersion = true
-			case "help":
+		case "-h":
+			fallthrough
+		case "--help":
 			parsed.ShowHelp = true
-			case "demand-press-enter":
+		case "--demand-press-enter":
 			parsed.DemandPressEnter = true
-			case "username":
+		case "-u":
+			fallthrough
+		case "--username":
 			if len(args) == i+1 || args[i+1][0] == '-' {
 				err = errNoOptArg{ArgName: args[i]}
 				return
 			}
 			parsed.Username = args[i+1]
 			i++
-			case "uuid":
+		case "-U":
+			fallthrough
+		case "--uuid":
 			if len(args) == i+1 || args[i+1][0] == '-' {
 				err = errNoOptArg{ArgName: args[i]}
 				return
 			}
 			parsed.Uuid = args[i+1]
 			i++
-			case "java-Xmx":
+		case "--java-Xmx":
 			if len(args) == i+1 || args[i+1][0] == '-' {
 				err = errNoOptArg{ArgName: args[i]}
 				return
 			}
 			parsed.JavaXmx = args[i+1]
 			i++
-			case "profile":
+		case "--profile":
 			parsed.UseProfile = true
 		default:
 			err = fmt.Errorf("an unknown option %s was provided", args[i])
 			return
 		}
-		} else if args[i][0] == '-' && len(args[i]) > 1 {
-			for _, option := range args[i][1:] {
-				switch option {
-				case 'v':
-					parsed.ShowVersion = true
-				case 'h':
-					parsed.ShowHelp = true
-				case 'u':
-					if len(args) == i+1 || args[i+1][0] == '-' {
-						err = errNoOptArg{ArgName: args[i]}
-						return
-					}
-					parsed.Username = args[i+1]
-					i++
-				case 'U':
-					if len(args) == i+1 || args[i+1][0] == '-' {
-						err = errNoOptArg{ArgName: args[i]}
-						return
-					}
-					parsed.Uuid = args[i+1]
-					i++
-				default:
-					err = fmt.Errorf("an unknown option %c was provided", option)
-					return
-				}
-			}
-		} else {
-			if parsed.Command != "" {
-				err = fmt.Errorf("only one command should present")
-				return
-			}
-			switch parsed.Command = args[i]; parsed.Command {
-			case "i":
-				fallthrough
-			case "install":
-				fallthrough
-			case "r":
-				fallthrough
-			case "run":
-				if len(args) <= i+3 || args[i+1][0] == '-' || args[i+2][0] == '-' {
-					err = fmt.Errorf("not enough arguments was provided")
-					return
-				}
-				parsed.GameVersion = args[i+1]
-				parsed.Directory = args[i+2]
-				i += 2
-			case "l":
-				fallthrough
-			case "list":
-				if len(args) <= i+2 || args[i+1][0] == '-' {
-					err = fmt.Errorf("not enough arguments was provided")
-					return
-				}
-				parsed.Directory = args[i+1]
-				i++
-			default:
-				err = fmt.Errorf("an unknown command %s was provided", parsed.Command)
-				return
-			}
-		}
 	}
 	return
 }