new sub-option for backup: time

New option to specify the timestamp for a backup

internal/archiver/testing.go

@@ -3,6 +3,7 @@ package archiver
 import (
 	"context"
 	"testing"
+	"time"
 
 	"github.com/restic/restic/internal/restic"
 )
@@ -10,7 +11,7 @@ import (
 // TestSnapshot creates a new snapshot of path.
 func TestSnapshot(t testing.TB, repo restic.Repository, path string, parent *restic.ID) *restic.Snapshot {
 	arch := New(repo)
-	sn, _, err := arch.Snapshot(context.TODO(), nil, []string{path}, []string{"test"}, "localhost", parent)
+	sn, _, err := arch.Snapshot(context.TODO(), nil, []string{path}, []string{"test"}, "localhost", parent, time.Now())
 	if err != nil {
 		t.Fatal(err)
 	}