Improve -generate-config handling

- do not print client version when running with the -generate-config option
- add a YAML document prefix before the raw YAML output
- use proper exit codes on errors

cmd/signerclient/main.go

@@ -18,9 +18,11 @@ limitations under the License.
 package main
 
 import (
+	"bytes"
 	"context"
 	"flag"
 	"fmt"
+	"io"
 	"os"
 	"strings"
 
@@ -54,8 +56,6 @@ func main() {
 	logger.SetOutput(os.Stdout)
 	logger.SetLevel(logrus.InfoLevel)
 
-	logger.Infof("cacert-gosignerclient %s (%s) - build %s", version, commit, date)
-
 	flag.StringVar(&configFile, "config", defaultConfigFile, "signer client configuration file")
 	flag.BoolVar(&showVersion, "version", false, "show version")
 	flag.BoolVar(&verbose, "verbose", false, "verbose output")
@@ -69,27 +69,31 @@ func main() {
 
 	flag.Parse()
 
-	if showVersion {
-		return
-	}
-
 	parsedLevel, err := logrus.ParseLevel(logLevel)
 	if err != nil {
 		logger.WithError(err).Fatal("could not parse log level")
 	}
 
-	logger.SetLevel(parsedLevel)
-
 	if generateConfig {
 		if err = generateDefaultConfig(); err != nil {
 			logger.WithError(err).Fatal("could not generate default configuration")
 		}
 
+		os.Exit(1)
+	}
+
+	logger.Infof("cacert-gosignerclient %s (%s) - build %s", version, commit, date)
+
+	if showVersion {
 		return
 	}
 
+	logger.SetLevel(parsedLevel)
+
 	if err := startClient(configFile, logger); err != nil {
 		logger.WithError(err).Fatal("client failure")
+
+		os.Exit(1)
 	}
 }
 
@@ -100,18 +104,26 @@ serial:
   baud: 112500
 `
 
-	cfg, err := config.LoadConfiguration(strings.NewReader(
-		defaultBaseConfiguration))
+	cfg, err := config.LoadConfiguration(strings.NewReader(defaultBaseConfiguration))
 	if err != nil {
 		return fmt.Errorf("could not load empty configuration: %w", err)
 	}
 
-	enc := yaml.NewEncoder(os.Stdout)
+	buf := &bytes.Buffer{}
+
+	buf.WriteString("---\n")
+
+	enc := yaml.NewEncoder(buf)
 
 	if err = enc.Encode(cfg); err != nil {
 		return fmt.Errorf("could not encode: %w", err)
 	}
 
+	_, err = io.Copy(os.Stdout, buf)
+	if err != nil {
+		return fmt.Errorf("could not write output: %w", err)
+	}
+
 	return nil
 }