errcheck: Add error checks

Most added checks are straight forward.

internal/repository/index_test.go

@@ -301,7 +301,11 @@ var (
 func initBenchmarkIndexJSON() {
 	idx, _ := createRandomIndex(rand.New(rand.NewSource(0)), 200000)
 	var buf bytes.Buffer
-	idx.Encode(&buf)
+	err := idx.Encode(&buf)
+	if err != nil {
+		panic(err)
+	}
+
 	benchmarkIndexJSON = buf.Bytes()
 }
 

internal/repository/master_index_test.go

@@ -338,7 +338,10 @@ func TestIndexSave(t *testing.T) {
 	repo, cleanup := createFilledRepo(t, 3, 0)
 	defer cleanup()
 
-	repo.LoadIndex(context.TODO())
+	err := repo.LoadIndex(context.TODO())
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	obsoletes, err := repo.Index().(*repository.MasterIndex).Save(context.TODO(), repo, nil, nil, nil)
 	if err != nil {

internal/repository/repack_test.go

@@ -201,7 +201,11 @@ func rebuildIndex(t *testing.T, repo restic.Repository) {
 }
 
 func reloadIndex(t *testing.T, repo restic.Repository) {
-	repo.SetIndex(repository.NewMasterIndex())
+	err := repo.SetIndex(repository.NewMasterIndex())
+	if err != nil {
+		t.Fatal(err)
+	}
+
 	if err := repo.LoadIndex(context.TODO()); err != nil {
 		t.Fatalf("error loading new index: %v", err)
 	}

internal/repository/repository.go

@@ -781,16 +781,19 @@ func DownloadAndHash(ctx context.Context, be Loader, h restic.Handle) (tmpfile *
 		hash = restic.IDFromHash(hrd.Sum(nil))
 		return ierr
 	})
+
 	if err != nil {
-		tmpfile.Close()
-		os.Remove(tmpfile.Name())
+		// ignore subsequent errors
+		_ = tmpfile.Close()
+		_ = os.Remove(tmpfile.Name())
 		return nil, restic.ID{}, -1, errors.Wrap(err, "Load")
 	}
 
 	_, err = tmpfile.Seek(0, io.SeekStart)
 	if err != nil {
-		tmpfile.Close()
-		os.Remove(tmpfile.Name())
+		// ignore subsequent errors
+		_ = tmpfile.Close()
+		_ = os.Remove(tmpfile.Name())
 		return nil, restic.ID{}, -1, errors.Wrap(err, "Seek")
 	}