migrations: move logic of upgrade_repo_v2 to repository package

The migration modifies repository internals and thus should live within
the repository package.

internal/migrations/upgrade_repo_v2_test.go

@@ -2,15 +2,9 @@ package migrations
 
 import (
 	"context"
-	"os"
-	"path/filepath"
-	"sync"
 	"testing"
 
-	"github.com/restic/restic/internal/backend"
-	"github.com/restic/restic/internal/errors"
 	"github.com/restic/restic/internal/repository"
-	"github.com/restic/restic/internal/test"
 )
 
 func TestUpgradeRepoV2(t *testing.T) {
@@ -35,73 +29,3 @@ func TestUpgradeRepoV2(t *testing.T) {
 		t.Fatal(err)
 	}
 }
-
-type failBackend struct {
-	backend.Backend
-
-	mu                        sync.Mutex
-	ConfigFileSavesUntilError uint
-}
-
-func (be *failBackend) Save(ctx context.Context, h backend.Handle, rd backend.RewindReader) error {
-	if h.Type != backend.ConfigFile {
-		return be.Backend.Save(ctx, h, rd)
-	}
-
-	be.mu.Lock()
-	if be.ConfigFileSavesUntilError == 0 {
-		be.mu.Unlock()
-		return errors.New("failure induced for testing")
-	}
-
-	be.ConfigFileSavesUntilError--
-	be.mu.Unlock()
-
-	return be.Backend.Save(ctx, h, rd)
-}
-
-func TestUpgradeRepoV2Failure(t *testing.T) {
-	be := repository.TestBackend(t)
-
-	// wrap backend so that it fails upgrading the config after the initial write
-	be = &failBackend{
-		ConfigFileSavesUntilError: 1,
-		Backend:                   be,
-	}
-
-	repo := repository.TestRepositoryWithBackend(t, be, 1, repository.Options{})
-	if repo.Config().Version != 1 {
-		t.Fatal("test repo has wrong version")
-	}
-
-	m := &UpgradeRepoV2{}
-
-	ok, _, err := m.Check(context.Background(), repo)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if !ok {
-		t.Fatal("migration check returned false")
-	}
-
-	err = m.Apply(context.Background(), repo)
-	if err == nil {
-		t.Fatal("expected error returned from Apply(), got nil")
-	}
-
-	upgradeErr := err.(*UpgradeRepoV2Error)
-	if upgradeErr.UploadNewConfigError == nil {
-		t.Fatal("expected upload error, got nil")
-	}
-
-	if upgradeErr.ReuploadOldConfigError == nil {
-		t.Fatal("expected reupload error, got nil")
-	}
-
-	if upgradeErr.BackupFilePath == "" {
-		t.Fatal("no backup file path found")
-	}
-	test.OK(t, os.Remove(upgradeErr.BackupFilePath))
-	test.OK(t, os.Remove(filepath.Dir(upgradeErr.BackupFilePath)))
-}