Be careful what you wish for

prog/weaver/main.go

@@ -3,7 +3,7 @@ package main
 import (
 	"crypto/sha256"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net"
 	"net/http"
 	_ "net/http/pprof"
@@ -27,6 +27,18 @@ import (
 
 var version = "(unreleased version)"
 
+type rewriter struct {
+	writer io.Writer
+}
+
+func (r rewriter) Write(p []byte) (int, error) {
+	if string(p) == "See '/home/weave/weaver  --help'.\n" {
+		return fmt.Fprintln(r.writer, "See 'weave help'.")
+	} else {
+		return r.writer.Write(p)
+	}
+}
+
 func main() {
 	procs := runtime.NumCPU()
 	// packet sniffing can block an OS thread, so we need one thread
@@ -63,8 +75,8 @@ func main() {
 		dnsClientTimeout   time.Duration
 	)
 
-	fs := mflag.NewFlagSet("", mflag.ContinueOnError)
-	fs.SetOutput(ioutil.Discard)
+	fs := mflag.NewFlagSet("", mflag.ExitOnError)
+	fs.SetOutput(rewriter{os.Stderr})
 	fs.BoolVar(&justVersion, []string{"#version", "-version"}, false, "print version and exit")
 	fs.IntVar(&config.Port, []string{"#port", "-port"}, weave.Port, "router port")
 	fs.IntVar(&protocolMinVersion, []string{"-min-protocol-version"}, weave.ProtocolMinVersion, "minimum weave protocol version")
@@ -90,9 +102,7 @@ func main() {
 	fs.IntVar(&dnsTTL, []string{"-dns-ttl"}, nameserver.DefaultTTL, "TTL for DNS request from our domain")
 	fs.DurationVar(&dnsClientTimeout, []string{"-dns-fallback-timeout"}, nameserver.DefaultClientTimeout, "timeout for fallback DNS requests")
 
-	if err := fs.Parse(os.Args[1:]); err != nil {
-		Log.Fatalf("Incorrect usage: %s", err)
-	}
+	fs.Parse(os.Args[1:])
 	SetLogLevel(logLevel)
 	peers = fs.Args()