A bunch of changes

Signed-off-by: Dave Henderson <dhenderson@gmail.com>

cmd/onerng/root.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+)
+
+var (
+	cfgFile string
+	opts    config
+)
+
+func rootCmd(ctx context.Context) *cobra.Command {
+	return &cobra.Command{
+		Use:   "onerng [opts] COMMAND",
+		Short: "Tool for the OneRNG open source hardware entropy generator",
+		Long: `OneRNG is an open source hardware entropy generator in a USB dongle.
+
+This tool can be used to verify that the OneRNG device operates
+correctly, and that the firmware has not been tampered with.`,
+		PersistentPreRunE: func(cmd *cobra.Command, args []string) error {
+			cmd.SilenceErrors = true
+			cmd.SilenceUsage = true
+			return nil
+		},
+	}
+}
+
+func initConfig(ctx context.Context, cmd *cobra.Command) {
+	cmd.PersistentFlags().StringVar(&cfgFile, "config", "", "config file (default is $HOME/.go-onerng.yaml)")
+	opts = config{}
+	cmd.PersistentFlags().StringVarP(&opts.Device, "device", "d", "/dev/ttyACM0", "the OneRNG device")
+
+	cmd.AddCommand(
+		verifyCmd(ctx),
+		versionCmd(ctx),
+		idCmd(ctx),
+		flushCmd(ctx),
+		imageCmd(ctx),
+		initCmd(ctx),
+		readCmd(ctx),
+	)
+
+	if cfgFile != "" { // enable ability to specify config file via flag
+		viper.SetConfigFile(cfgFile)
+	}
+
+	viper.SetConfigName(".go-onerng")      // name of config file (without extension)
+	viper.AddConfigPath(os.Getenv("HOME")) // adding home directory as first search path
+	viper.AutomaticEnv()                   // read in environment variables that match
+
+	// If a config file is found, read it in.
+	if err := viper.ReadInConfig(); err == nil {
+		fmt.Fprintln(os.Stderr, "Using config file:", viper.ConfigFileUsed())
+	}
+}
+
+type config struct {
+	Device string
+}