Only show parse errors and command to invoke usage.

Rather than showing the usage when an error is encounted during options
parsing, show a message that describes how to invoke help instead.  This
is useful because the help is long enough now that the error is often
overlooked since it scrolls out of view.

ok @jrick

config.go

@@ -333,9 +333,10 @@ func loadConfig() (*config, []string, error) {
 	preParser.Parse()
 
 	// Show the version and exit if the version flag was specified.
-	if preCfg.ShowVersion {
 	appName := filepath.Base(os.Args[0])
 	appName = strings.TrimSuffix(appName, filepath.Ext(appName))
+	usageMessage := fmt.Sprintf("Use %s -h to show usage", appName)
+	if preCfg.ShowVersion {
 		fmt.Println(appName, "version", version())
 		os.Exit(0)
 	}
@@ -360,8 +361,9 @@ func loadConfig() (*config, []string, error) {
 		err := flags.NewIniParser(parser).ParseFile(preCfg.ConfigFile)
 		if err != nil {
 			if _, ok := err.(*os.PathError); !ok {
-				fmt.Fprintln(os.Stderr, err)
+				fmt.Fprintf(os.Stderr, "Error parsing config "+
-				parser.WriteHelp(os.Stderr)
+					"file: %v\n", err)
+				fmt.Fprintln(os.Stderr, usageMessage)
 				return nil, nil, err
 			}
 			configFileError = err
@@ -377,7 +379,7 @@ func loadConfig() (*config, []string, error) {
 	remainingArgs, err := parser.Parse()
 	if err != nil {
 		if e, ok := err.(*flags.Error); !ok || e.Type != flags.ErrHelp {
-			parser.WriteHelp(os.Stderr)
+			fmt.Fprintln(os.Stderr, usageMessage)
 		}
 		return nil, nil, err
 	}
@@ -399,7 +401,7 @@ func loadConfig() (*config, []string, error) {
 			"used together -- choose one of the three"
 		err := fmt.Errorf(str, funcName)
 		fmt.Fprintln(os.Stderr, err)
-		parser.WriteHelp(os.Stderr)
+		fmt.Fprintln(os.Stderr, usageMessage)
 		return nil, nil, err
 	}
 
@@ -443,7 +445,7 @@ func loadConfig() (*config, []string, error) {
 	if err := parseAndSetDebugLevels(cfg.DebugLevel); err != nil {
 		err := fmt.Errorf("%s: %v", funcName, err.Error())
 		fmt.Fprintln(os.Stderr, err)
-		parser.WriteHelp(os.Stderr)
+		fmt.Fprintln(os.Stderr, usageMessage)
 		return nil, nil, err
 	}
 
@@ -453,7 +455,7 @@ func loadConfig() (*config, []string, error) {
 			"supported types %v"
 		err := fmt.Errorf(str, funcName, cfg.DbType, knownDbTypes)
 		fmt.Fprintln(os.Stderr, err)
-		parser.WriteHelp(os.Stderr)
+		fmt.Fprintln(os.Stderr, usageMessage)
 		return nil, nil, err
 	}
 
@@ -464,7 +466,7 @@ func loadConfig() (*config, []string, error) {
 			str := "%s: The profile port must be between 1024 and 65535"
 			err := fmt.Errorf(str, funcName)
 			fmt.Fprintln(os.Stderr, err)
-			parser.WriteHelp(os.Stderr)
+			fmt.Fprintln(os.Stderr, usageMessage)
 			return nil, nil, err
 		}
 	}
@@ -474,7 +476,7 @@ func loadConfig() (*config, []string, error) {
 		str := "%s: The banduration option may not be less than 1s -- parsed [%v]"
 		err := fmt.Errorf(str, funcName, cfg.BanDuration)
 		fmt.Fprintln(os.Stderr, err)
-		parser.WriteHelp(os.Stderr)
+		fmt.Fprintln(os.Stderr, usageMessage)
 		return nil, nil, err
 	}
 
@@ -484,7 +486,7 @@ func loadConfig() (*config, []string, error) {
 			"mixed"
 		err := fmt.Errorf(str, funcName)
 		fmt.Fprintln(os.Stderr, err)
-		parser.WriteHelp(os.Stderr)
+		fmt.Fprintln(os.Stderr, usageMessage)
 		return nil, nil, err
 	}
 
@@ -536,7 +538,7 @@ func loadConfig() (*config, []string, error) {
 		err := fmt.Errorf(str, funcName, blockMaxSizeMin,
 			blockMaxSizeMax, cfg.BlockMaxSize)
 		fmt.Fprintln(os.Stderr, err)
-		parser.WriteHelp(os.Stderr)
+		fmt.Fprintln(os.Stderr, usageMessage)
 		return nil, nil, err
 	}
 
@@ -554,14 +556,14 @@ func loadConfig() (*config, []string, error) {
 			str := "%s: getworkkey '%s' failed to decode: %v"
 			err := fmt.Errorf(str, funcName, strAddr, err)
 			fmt.Fprintln(os.Stderr, err)
-			parser.WriteHelp(os.Stderr)
+			fmt.Fprintln(os.Stderr, usageMessage)
 			return nil, nil, err
 		}
 		if !addr.IsForNet(activeNetParams.Params) {
 			str := "%s: getworkkey '%s' is on the wrong network"
 			err := fmt.Errorf(str, funcName, strAddr)
 			fmt.Fprintln(os.Stderr, err)
-			parser.WriteHelp(os.Stderr)
+			fmt.Fprintln(os.Stderr, usageMessage)
 			return nil, nil, err
 		}
 		cfg.miningAddrs = append(cfg.miningAddrs, addr)
@@ -574,14 +576,14 @@ func loadConfig() (*config, []string, error) {
 			str := "%s: mining address '%s' failed to decode: %v"
 			err := fmt.Errorf(str, funcName, strAddr, err)
 			fmt.Fprintln(os.Stderr, err)
-			parser.WriteHelp(os.Stderr)
+			fmt.Fprintln(os.Stderr, usageMessage)
 			return nil, nil, err
 		}
 		if !addr.IsForNet(activeNetParams.Params) {
 			str := "%s: mining address '%s' is on the wrong network"
 			err := fmt.Errorf(str, funcName, strAddr)
 			fmt.Fprintln(os.Stderr, err)
-			parser.WriteHelp(os.Stderr)
+			fmt.Fprintln(os.Stderr, usageMessage)
 			return nil, nil, err
 		}
 		cfg.miningAddrs = append(cfg.miningAddrs, addr)
@@ -594,7 +596,7 @@ func loadConfig() (*config, []string, error) {
 			"addresses specified "
 		err := fmt.Errorf(str, funcName)
 		fmt.Fprintln(os.Stderr, err)
-		parser.WriteHelp(os.Stderr)
+		fmt.Fprintln(os.Stderr, usageMessage)
 		return nil, nil, err
 	}