Validate restore name label length

Velero should handle cases when the label length exceeds 63 characters.

- if the length of the backup/restore name is <= 63 characters, use it as the value of the label
- if it's > 63 characters, take the SHA256 hash of the name. the value of
  the label will be the first 57 characters of the backup/restore name
  plus the first six characters of the SHA256 hash.

Fixes heptio#1021

Signed-off-by: Anshul Chandra <anshulc@vmware.com>

pkg/controller/gc_controller.go

@@ -31,6 +31,7 @@ import (
 	velerov1client "github.com/heptio/velero/pkg/generated/clientset/versioned/typed/velero/v1"
 	informers "github.com/heptio/velero/pkg/generated/informers/externalversions/velero/v1"
 	listers "github.com/heptio/velero/pkg/generated/listers/velero/v1"
+	"github.com/heptio/velero/pkg/label"
 )
 
 const (
@@ -133,7 +134,7 @@ func (c *gcController) processQueueItem(key string) error {
 	log.Info("Backup has expired")
 
 	selector := labels.SelectorFromSet(labels.Set(map[string]string{
-		velerov1api.BackupNameLabel: backup.Name,
+		velerov1api.BackupNameLabel: label.GetValidName(backup.Name),
 		velerov1api.BackupUIDLabel:  string(backup.UID),
 	}))