convert MemorizeList to be repository based

Ideally, code that uses a repository shouldn't directly interact with
the underlying backend. Thus, move MemorizeList one layer up.

internal/backend/utils.go

@@ -74,44 +74,3 @@ type LimitedReadCloser struct {
 func LimitReadCloser(r io.ReadCloser, n int64) *LimitedReadCloser {
 	return &LimitedReadCloser{Closer: r, LimitedReader: io.LimitedReader{R: r, N: n}}
 }
-
-type memorizedLister struct {
-	fileInfos []FileInfo
-	tpe       FileType
-}
-
-func (m *memorizedLister) List(ctx context.Context, t FileType, fn func(FileInfo) error) error {
-	if t != m.tpe {
-		return fmt.Errorf("filetype mismatch, expected %s got %s", m.tpe, t)
-	}
-	for _, fi := range m.fileInfos {
-		if ctx.Err() != nil {
-			break
-		}
-		err := fn(fi)
-		if err != nil {
-			return err
-		}
-	}
-	return ctx.Err()
-}
-
-func MemorizeList(ctx context.Context, be Lister, t FileType) (Lister, error) {
-	if _, ok := be.(*memorizedLister); ok {
-		return be, nil
-	}
-
-	var fileInfos []FileInfo
-	err := be.List(ctx, t, func(fi FileInfo) error {
-		fileInfos = append(fileInfos, fi)
-		return nil
-	})
-	if err != nil {
-		return nil, err
-	}
-
-	return &memorizedLister{
-		fileInfos: fileInfos,
-		tpe:       t,
-	}, nil
-}