'wdcli backup': Rework backup process

This commit reworks the backup process to dynamically find the list of
components.

internal/component/control/backup.go

@@ -0,0 +1,48 @@
+package control
+
+import (
+	"io/fs"
+	"os"
+	"path/filepath"
+
+	"github.com/FAU-CDI/wisski-distillery/pkg/fsx"
+	"github.com/tkw1536/goprogram/stream"
+)
+
+func (*Control) BackupName() string {
+	return "config"
+}
+
+// Backup backups all control plane configuration files into dest
+func (control *Control) Backup(io stream.IOStream, dest string) error {
+	// create the destination directory, TODO: outsource this
+	if err := os.Mkdir(dest, fs.ModeDir); err != nil {
+		return err
+	}
+
+	files := control.backupFiles()
+	for _, src := range files {
+		dst := filepath.Join(dest, filepath.Base(src)) // destination path
+
+		// if the src file does not exist, don't copy it!
+		if !fsx.IsFile(src) { // TODO: log this somewhere
+			continue
+		}
+
+		if err := fsx.CopyFile(dst, src); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// backupfiles lists the files to be backed up.
+func (control *Control) backupFiles() []string {
+	return []string{
+		control.Config.ConfigPath,
+		control.Config.ExecutablePath(),
+		control.Config.SelfOverridesFile,
+		control.Config.GlobalAuthorizedKeysFile,
+	}
+}