feat(cmd): shell completion subcommand (#576)

Co-authored-by: Sumire (菫) <[email protected]>

cmd/completion.go

@@ -0,0 +1,59 @@
+/*
+ * SPDX-License-Identifier: AGPL-3.0-only
+ * Copyright (c) 2022-2024, daeuniverse Organization <[email protected]>
+ */
+
+package cmd
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+
+	"github.com/spf13/cobra"
+)
+
+var (
+	completionCmd = &cobra.Command{
+		Use:       "completion [bash|zsh|fish]",
+		Short:     "Output shell completion code for the specified shell (bash, zsh or fish)",
+		Long:      "Output shell completion code for the specified shell (bash, zsh or fish).",
+		Args:      cobra.ExactArgs(1),
+		ValidArgs: []string{"bash", "zsh", "fish"},
+		Hidden:    true,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			out, err := getCompletion(args[0], cmd.Parent())
+			if err != nil {
+				return err
+			}
+
+			fmt.Print(out)
+			return nil
+		},
+	}
+)
+
+// return the auto completion shell script, if supported
+func getCompletion(sh string, parent *cobra.Command) (string, error) {
+	var err error
+	var buf bytes.Buffer
+
+	switch sh {
+	case "bash":
+		err = parent.GenBashCompletion(&buf)
+	case "zsh":
+		err = parent.GenZshCompletion(&buf)
+	case "fish":
+		err = parent.GenFishCompletion(&buf, true)
+	default:
+		err = errors.New("unsupported shell type (must be bash, zsh or fish): " + sh)
+	}
+
+	if err != nil {
+		return "", err
+	}
+	return buf.String(), nil
+}
+func init() {
+	rootCmd.AddCommand(completionCmd)
+}

cmd/run.go

@@ -55,7 +55,7 @@ var (
 )
 
 func init() {
-	runCmd.PersistentFlags().StringVarP(&cfgFile, "config", "c", "", "Config file of dae.")
+	runCmd.PersistentFlags().StringVarP(&cfgFile, "config", "c", "", "Config file of dae.(required)")
 	runCmd.PersistentFlags().StringVar(&logFile, "logfile", "", "Log file to write. Empty means writing to stdout and stderr.")
 	runCmd.PersistentFlags().IntVar(&logFileMaxSize, "logfile-maxsize", 30, "Unit: MB. The maximum size in megabytes of the log file before it gets rotated.")
 	runCmd.PersistentFlags().IntVar(&logFileMaxBackups, "logfile-maxbackups", 3, "The maximum number of old log files to retain.")