R4R: add command to generate bash completion for gaia{d,cli}

PENDING.md

@@ -61,6 +61,7 @@ FEATURES
   * [\#3198](https://github.com/cosmos/cosmos-sdk/issues/3198) New `multisign` command to generate multisig signatures.
   * [\#3198](https://github.com/cosmos/cosmos-sdk/issues/3198) New `sign --multisig` flag to enable multisig mode.
   * [\#2715](https://github.com/cosmos/cosmos-sdk/issues/2715) Reintroduce gaia server's insecure mode.
+  * [\#3334](https://github.com/cosmos/cosmos-sdk/pull/3334) New `gaiad completion` and `gaiacli completion` to generate Bash/Zsh completion scripts.
 
 * Gaia
   * [\#2182] [x/staking] Added querier for querying a single redelegation

client/flags.go

@@ -2,6 +2,7 @@ package client
 
 import (
 	"fmt"
+	"os"
 	"strconv"
 
 	"github.com/spf13/cobra"
@@ -162,3 +163,35 @@ func ParseGas(gasStr string) (simulateAndExecute bool, gas uint64, err error) {
 	}
 	return
 }
+
+// NewCompletionCmd builds a cobra.Command that generate bash completion
+// scripts for the given root command. If hidden is true, the command
+// will not show up in the root command's list of available commands.
+func NewCompletionCmd(rootCmd *cobra.Command, hidden bool) *cobra.Command {
+	flagZsh := "zsh"
+	cmd := &cobra.Command{
+		Use:   "completion",
+		Short: "Generate Bash/Zsh completion script to STDOUT",
+		Long: `To load completion script run
+
+. <(completion_script)
+
+To configure your bash shell to load completions for each session add to your bashrc
+
+# ~/.bashrc or ~/.profile
+. <(completion_script)
+`,
+		RunE: func(_ *cobra.Command, _ []string) error {
+			if viper.GetBool(flagZsh) {
+				return rootCmd.GenZshCompletion(os.Stdout)
+			}
+			return rootCmd.GenBashCompletion(os.Stdout)
+		},
+		Hidden: hidden,
+		Args:   cobra.NoArgs,
+	}
+
+	cmd.Flags().Bool(flagZsh, false, "Generate Zsh completion script")
+
+	return cmd
+}

cmd/gaia/cmd/gaiacli/main.go

@@ -93,6 +93,7 @@ func main() {
 		keys.Commands(),
 		client.LineBreak,
 		version.VersionCmd,
+		client.NewCompletionCmd(rootCmd, true),
 	)
 
 	// Add flags and prefix all env exposed with GA

cmd/gaia/cmd/gaiad/main.go

@@ -14,6 +14,7 @@ import (
 	tmtypes "github.com/tendermint/tendermint/types"
 
 	"github.com/cosmos/cosmos-sdk/baseapp"
+	"github.com/cosmos/cosmos-sdk/client"
 	"github.com/cosmos/cosmos-sdk/cmd/gaia/app"
 	gaiaInit "github.com/cosmos/cosmos-sdk/cmd/gaia/init"
 	"github.com/cosmos/cosmos-sdk/server"
@@ -42,6 +43,7 @@ func main() {
 	rootCmd.AddCommand(gaiaInit.TestnetFilesCmd(ctx, cdc))
 	rootCmd.AddCommand(gaiaInit.GenTxCmd(ctx, cdc))
 	rootCmd.AddCommand(gaiaInit.AddGenesisAccountCmd(ctx, cdc))
+	rootCmd.AddCommand(client.NewCompletionCmd(rootCmd, true))
 
 	server.AddCommands(ctx, cdc, rootCmd, newApp, exportAppStateAndTMValidators)
 

docs/gaia/gaiacli.md

@@ -761,3 +761,36 @@ The transaction can now be sent to the node:
 ```bash
 gaiacli tx broadcast signedTx.json
 ```
+
+## Shells completion scripts
+
+Completion scripts for popular UNIX shell interpreters such as `Bash` and `Zsh`
+can be generated through the `completion` command, which is available for both
+`gaiad` and `gaiacli`.
+
+If you want to generate `Bash` completion scripts run the following command:
+
+```bash
+gaiad completion > gaiad_completion
+gaiacli completion > gaiacli_completion
+```
+
+If you want to generate `Zsh` completion scripts run the following command:
+
+```bash
+gaiad completion --zsh > gaiad_completion
+gaiacli completion --zsh > gaiacli_completion
+```
+
+::: tip Note
+On most UNIX systems, such scripts may be loaded in `.bashrc` or
+`.bash_profile` to enable Bash autocompletion:
+
+```bash
+echo '. gaiad_completion' >> ~/.bashrc
+echo '. gaiacli_completion' >> ~/.bashrc
+```
+
+Refer to the user's manual of your interpreter provided by your
+operating system for information on how to enable shell autocompletion.
+:::