Add backup-version file in backup tarball

Signed-off-by: Wayne Witzel III <wayne@riotousliving.com>

pkg/backup/backup.go

@@ -41,6 +41,9 @@ import (
 	kubeutil "github.com/heptio/ark/pkg/util/kube"
 )
 
+// BackupVersion is the current backup version for Ark.
+const BackupVersion = "1.0.0"
+
 // Backupper performs backups.
 type Backupper interface {
 	// Backup takes a backup using the specification in the api.Backup and writes backup and log data
@@ -221,6 +224,10 @@ func (kb *kubernetesBackupper) Backup(logger logrus.FieldLogger, backupRequest *
 	log := logger.WithField("backup", kubeutil.NamespaceAndName(backupRequest))
 	log.Info("Starting backup")
 
+	if err := kb.writeBackupVersion(tw); err != nil {
+		return errors.WithStack(err)
+	}
+
 	backupRequest.NamespaceIncludesExcludes = getNamespaceIncludesExcludes(backupRequest.Backup)
 	log.Infof("Including namespaces: %s", backupRequest.NamespaceIncludesExcludes.IncludesString())
 	log.Infof("Excluding namespaces: %s", backupRequest.NamespaceIncludesExcludes.ExcludesString())
@@ -292,6 +299,23 @@ func (kb *kubernetesBackupper) Backup(logger logrus.FieldLogger, backupRequest *
 	return err
 }
 
+func (kb *kubernetesBackupper) writeBackupVersion(tw *tar.Writer) error {
+	hdr := &tar.Header{
+		Name:     "backup-version",
+		Size:     int64(len(BackupVersion)),
+		Typeflag: tar.TypeReg,
+		Mode:     0644,
+		ModTime:  time.Now(),
+	}
+	if err := tw.WriteHeader(hdr); err != nil {
+		return err
+	}
+	if _, err := tw.Write([]byte(BackupVersion)); err != nil {
+		return err
+	}
+	return nil
+}
+
 type tarWriter interface {
 	io.Closer
 	Write([]byte) (int, error)