Merge PR #3316: Fix regression in gaiacli config file handling

* --chain-id must be a persistent flag to be successfully read from config
* Prevent panic when not enough arguments
* Add docs on gaiacli config
* Small tweak

cmd/gaia/cli_test/test_helpers.go

@@ -98,6 +98,7 @@ func InitFixtures(t *testing.T) (f *Fixtures) {
 
 	// NOTE: GDInit sets the ChainID
 	f.GDInit(keyFoo)
+	f.CLIConfig("chain-id", f.ChainID)
 
 	// Start an account with tokens
 	f.AddGenesisAccount(f.KeyAddress(keyFoo), startCoins)
@@ -117,7 +118,7 @@ func (f *Fixtures) Cleanup(dirs ...string) {
 
 // Flags returns the flags necessary for making most CLI calls
 func (f *Fixtures) Flags() string {
-	return fmt.Sprintf("--home=%s --node=%s --chain-id=%s", f.GCLIHome, f.RPCAddr, f.ChainID)
+	return fmt.Sprintf("--home=%s --node=%s", f.GCLIHome, f.RPCAddr)
 }
 
 //___________________________________________________________________________________

cmd/gaia/cmd/gaiacli/main.go

@@ -75,6 +75,12 @@ func main() {
 		Short: "Command line interface for interacting with gaiad",
 	}
 
+	// Add --chain-id to persistent flags and mark it required
+	rootCmd.PersistentFlags().String(client.FlagChainID, "", "Chain ID of tendermint node")
+	rootCmd.PersistentPreRunE = func(_ *cobra.Command, _ []string) error {
+		return initConfig(rootCmd)
+	}
+
 	// Construct Root Command
 	rootCmd.AddCommand(
 		rpc.StatusCommand(),
@@ -91,12 +97,8 @@ func main() {
 
 	// Add flags and prefix all env exposed with GA
 	executor := cli.PrepareMainCmd(rootCmd, "GA", app.DefaultCLIHome)
-	err := initConfig(rootCmd)
-	if err != nil {
-		panic(err)
-	}
 
-	err = executor.Execute()
+	err := executor.Execute()
 	if err != nil {
 		fmt.Printf("Failed executing CLI command: %s, exiting...\n", err)
 		os.Exit(1)
@@ -186,7 +188,9 @@ func initConfig(cmd *cobra.Command) error {
 			return err
 		}
 	}
-
+	if err := viper.BindPFlag(client.FlagChainID, cmd.PersistentFlags().Lookup(client.FlagChainID)); err != nil {
+		return err
+	}
 	if err := viper.BindPFlag(cli.EncodingFlag, cmd.PersistentFlags().Lookup(cli.EncodingFlag)); err != nil {
 		return err
 	}