Handle broken cache manifest

internal/dl/dl.go

@@ -91,9 +91,7 @@ func Download(ctx context.Context, opts Options) (err error) {
 		}
 
 		m, err := getManifest(cacheDir)
-		if err != nil {
-			return err
-		}
+		if err == nil {
 			t = m.Type
 
 			dest := filepath.Join(opts.Destination, m.Name)
@@ -108,6 +106,15 @@ func Download(ctx context.Context, opts Options) (err error) {
 			} else if ok {
 				return nil
 			}
+		} else {
+			// If we cannot read the manifest,
+			// this cache entry is invalid and
+			// the source must be re-downloaded.
+			err = os.RemoveAll(cacheDir)
+			if err != nil {
+				return err
+			}
+		}
 	}
 
 	log.Info("Downloading source").Str("source", opts.Name).Str("downloader", d.Name()).Send()