add integration test for headscale -c

cmd/headscale/cli/dump_config.go

@@ -0,0 +1,28 @@
+package cli
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+)
+
+func init() {
+	rootCmd.AddCommand(dumpConfigCmd)
+}
+
+var dumpConfigCmd = &cobra.Command{
+	Use:    "dumpConfig",
+	Short:  "dump current config to /etc/headscale/config.dump.yaml, integration test only",
+	Hidden: true,
+	Args: func(cmd *cobra.Command, args []string) error {
+		return nil
+	},
+	Run: func(cmd *cobra.Command, args []string) {
+		err := viper.WriteConfigAs("/etc/headscale/config.dump.yaml")
+		if err != nil {
+			//nolint
+			fmt.Println("Failed to dump config")
+		}
+	},
+}