make Lookup() return all blobs

+ simplify syntax

cmd/restic/cmd_cat.go

@@ -165,8 +165,7 @@ func runCat(gopts GlobalOptions, args []string) error {
 
 	case "blob":
 		for _, t := range []restic.BlobType{restic.DataBlob, restic.TreeBlob} {
-			_, found := repo.Index().Lookup(id, t)
-			if !found {
+			if !repo.Index().Has(id, t) {
 				continue
 			}
 

cmd/restic/cmd_find.go

@@ -465,8 +465,8 @@ func (f *Finder) findObjectPack(ctx context.Context, id string, t restic.BlobTyp
 		return
 	}
 
-	blobs, found := idx.Lookup(rid, t)
-	if !found {
+	blobs := idx.Lookup(rid, t)
+	if len(blobs) == 0 {
 		Printf("Object %s not found in the index\n", rid.Str())
 		return
 	}