Fix: shell-completion (#2006)

* fix: shell-completion

* update: description

cmd/completion.go

@@ -0,0 +1,62 @@
+package cmd
+
+import (
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+var completionCmd = &cobra.Command{
+	Use:     "completion [bash|zsh|fish|powershell]",
+	Aliases: []string{"shell-completion"},
+	Short:   "Generate the autocompletion script for the specified shell",
+	Long: `To load completions:
+
+Bash:
+
+$ source <(yq completion bash)
+
+# To load completions for each session, execute once:
+Linux:
+  $ yq completion bash > /etc/bash_completion.d/yq
+MacOS:
+  $ yq completion bash > /usr/local/etc/bash_completion.d/yq
+
+Zsh:
+
+# If shell completion is not already enabled in your environment you will need
+# to enable it.  You can execute the following once:
+
+$ echo "autoload -U compinit; compinit" >> ~/.zshrc
+
+# To load completions for each session, execute once:
+$ yq completion zsh > "${fpath[1]}/_yq"
+
+# You will need to start a new shell for this setup to take effect.
+
+Fish:
+
+$ yq completion fish | source
+
+# To load completions for each session, execute once:
+$ yq completion fish > ~/.config/fish/completions/yq.fish
+`,
+	DisableFlagsInUseLine: true,
+	ValidArgs:             []string{"bash", "zsh", "fish", "powershell"},
+	Args:                  cobra.MatchAll(cobra.ExactArgs(1), cobra.OnlyValidArgs),
+	RunE: func(cmd *cobra.Command, args []string) error {
+		var err error = nil
+		switch args[0] {
+		case "bash":
+			err = cmd.Root().GenBashCompletionV2(os.Stdout, true)
+		case "zsh":
+			err = cmd.Root().GenZshCompletion(os.Stdout)
+		case "fish":
+			err = cmd.Root().GenFishCompletion(os.Stdout, true)
+		case "powershell":
+			err = cmd.Root().GenPowerShellCompletion(os.Stdout)
+		}
+		return err
+
+	},
+}