repository: Remove RunWorkers, report ctx.Err()

This removes RunWorkers, which had become mere overhead by successive
refactors. It also ensures that each former user of that function
returns any context error that occurs, so failure to complete an
operation is always reported as an error.

internal/repository/repository.go

@@ -679,7 +679,7 @@ func (r *Repository) CreateIndexFromPacks(ctx context.Context, packsize map[rest
 		for id, size := range packsize {
 			select {
 			case <-ctx.Done():
-				return nil
+				return ctx.Err()
 			case ch <- FileInfo{id, size}:
 			}
 		}
@@ -705,9 +705,9 @@ func (r *Repository) CreateIndexFromPacks(ctx context.Context, packsize map[rest
 	}
 
 	// run workers on ch
-	wg.Go(func() error {
-		return RunWorkers(listPackParallelism, worker)
-	})
+	for i := 0; i < listPackParallelism; i++ {
+		wg.Go(worker)
+	}
 
 	err = wg.Wait()
 	if err != nil {