flags : return HelpError and print at the callsite

sort/sort.go

@@ -1,6 +1,7 @@
 package sort
 
 import (
+	"errors"
 	"fmt"
 	"log"
 	"os"
@@ -69,11 +70,18 @@ func write(file string, content string) {
 
 func Sort(args []string) {
 	opts := initOpts()
-	flags.ParseArgs(CMD, SUMMARY, args, &opts)
+	if err := flags.ParseArgs(CMD, SUMMARY, args, &opts); err != nil {
+		var herr flags.HelpError
+		if errors.As(err, &herr) {
+			fmt.Println(herr)
+			return
+		}
+		log.Fatalf("um %s: %s", CMD, err)
+	}
 	// BORK: by hand for now:
 	if !opts.Key.IsSet() {
-		flags.HelpRequired(CMD, opts.Key.Long)
-		flags.Help(CMD, SUMMARY, opts)
+		fmt.Println(flags.HelpRequired(CMD, opts.Key.Long))
+		return
 	}
 
 	sslice, err := pipe.FileListSplitMaybeStdin(opts.Source.Val)