bash completions: hidden subcommand + integrate into Makefile

cmd/bashcomp.go

@@ -0,0 +1,29 @@
+package cmd
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+	"os"
+)
+
+var bashcompCmd = &cobra.Command{
+	Use:   "bashcomp path/to/out/file",
+	Short: "generate bash completions",
+	Run: func(cmd *cobra.Command, args []string) {
+		if len(args) != 1 {
+			fmt.Fprintf(os.Stderr, "specify exactly one positional agument\n")
+			cmd.Usage()
+			os.Exit(1)
+		}
+		if err := RootCmd.GenBashCompletionFile(args[0]); err != nil {
+			fmt.Fprintf(os.Stderr, "error generating bash completion: %s", err)
+			os.Exit(1)
+		}
+	},
+	Hidden: true,
+}
+
+func init() {
+	RootCmd.AddCommand(bashcompCmd)
+}