cmd/geth: add dumpgenesis command

I have a hard time believing this doesn't already exist...
although I could not find it anywhere.

cmd/geth/chaincmd.go

@@ -56,6 +56,21 @@ This is a destructive action and changes the network in which you will be
 participating.
 
 It expects the genesis file as argument.`,
+	}
+	dumpGenesisCommand = cli.Command{
+		Action:    utils.MigrateFlags(dumpGenesis),
+		Name:      "dumpgenesis",
+		Usage:     "Dumps genesis block JSON configuration to stdout",
+		ArgsUsage: "",
+		Flags: []cli.Flag{
+			utils.DataDirFlag,
+		},
+		Category: "BLOCKCHAIN COMMANDS",
+		Description: `
+The dumpgenesis command dumps the genesis block configuration in JSON format to stdout.
+
+This data can be used as a template or passed to the 'init' command. 
+`,
 	}
 	importCommand = cli.Command{
 		Action:    utils.MigrateFlags(importChain),
@@ -227,6 +242,14 @@ func initGenesis(ctx *cli.Context) error {
 	return nil
 }
 
+func dumpGenesis(ctx *cli.Context) error {
+	genesis := utils.MakeGenesis(ctx)
+	if err := json.NewEncoder(os.Stdout).Encode(genesis); err != nil {
+		utils.Fatalf("could not encode defaulty genesis")
+	}
+	return nil
+}
+
 func importChain(ctx *cli.Context) error {
 	if len(ctx.Args()) < 1 {
 		utils.Fatalf("This command requires an argument.")

cmd/geth/main.go

@@ -208,6 +208,7 @@ func init() {
 		copydbCommand,
 		removedbCommand,
 		dumpCommand,
+		dumpGenesisCommand,
 		inspectCommand,
 		// See accountcmd.go:
 		accountCommand,