type Migrator struct {
	cfg           *EtcdMigrateCfg // TODO: don't wire this directly in
	dataDirectory *DataDirectory
	client        EtcdMigrateClient
}

// MigrateIfNeeded upgrades or downgrades the etcd data directory to the given target version.
func (m *Migrator) MigrateIfNeeded(target *EtcdVersionPair) error {
	klog.Infof("Starting migration to %s", target)
	err := m.dataDirectory.Initialize(target)

				// If this conflict was just one step in a longer chain of downgrades,
				// then we would want to keep going past it until we find a version
				// that doesn't have that problem. However, we only want to downgrade
				// away from an *existing* requirement if we can confirm that it actually
				// conflicts with mustSelect. (For example, we don't want
				// 'go get -u ./...' to incidentally downgrade some dependency whose

		}
	}

	// kubeadm doesn't support downgrades between two minor versions; e.g. a v1.9 -> v1.7 downgrade is not supported right away
	if newK8sVersion.Minor() < clusterVersion.Minor()-MaximumAllowedMinorVersionDowngradeSkew {
		tooLargeDowngradeSkewErr := errors.Errorf("Specified version to downgrade to %q is too low; kubeadm can downgrade only %d minor version at a time", newK8sVersionStr, MaximumAllowedMinorVersionDowngradeSkew)

	// Current version being written.
	xlVersionCurrent [4]byte
)

const (
	// Breaking changes.
	// Newer versions cannot be read by older software.
	// This will prevent downgrades to incompatible versions.
	xlVersionMajor = 1

	// Non breaking changes.
	// Bumping this is informational, but should be done
	// if any change is made to the data stored, bumping this

        "ReadWriteC -> ReadWriteA",
        "ReadWriteB -> ReadWriteC",
        "ReadWriteA -> ReadWriteB");
  }

  public void testWriteToReadLockDowngrading() {
    writeLockA.lock(); // writeLockA downgrades to readLockA
    readLockA.lock();
    writeLockA.unlock();

    lockB.lock(); // readLockA -> lockB
    readLockA.unlock();

    // lockB -> writeLockA should fail

        "ReadWriteC -> ReadWriteA",
        "ReadWriteB -> ReadWriteC",
        "ReadWriteA -> ReadWriteB");
  }

  public void testWriteToReadLockDowngrading() {
    writeLockA.lock(); // writeLockA downgrades to readLockA
    readLockA.lock();
    writeLockA.unlock();

    lockB.lock(); // readLockA -> lockB
    readLockA.unlock();

    // lockB -> writeLockA should fail

				//
				// Go 1.21 also introduced the feature of allowing //go:build lines
				// to “downgrade” (cmp < 0) the Go version in a given file.
				// That can't be done compatibly in general, since before the
				// build lines were ignored and code got the module's Go version.
				// To work around this, downgrades are only allowed when the
				// module's Go version is Go 1.21 or later.
				//

				//
				// Go 1.21 also introduced the feature of allowing //go:build lines
				// to “downgrade” (cmp < 0) the Go version in a given file.
				// That can't be done compatibly in general, since before the
				// build lines were ignored and code got the module's Go version.
				// To work around this, downgrades are only allowed when the
				// module's Go version is Go 1.21 or later.
				//

	// Current version being written.
	xlVersionCurrent [4]byte
)

const (
	// Breaking changes.
	// Newer versions cannot be read by older software.
	// This will prevent downgrades to incompatible versions.
	xlVersionMajor = 1

	// Non breaking changes.
	// Bumping this is informational, but should be done
	// if any change is made to the data stored, bumping this

				v := module.Version{Path: q.pattern}
				// The user has explicitly requested to downgrade their own module to
				// version "none". This is not an entirely unreasonable request: it
				// could plausibly mean “downgrade away everything that depends on any
				// explicit version of the main module”, or “downgrade away the
				// package with the same path as the main module, found in a module