#   \      \
#    \      \
#     ----- c.1 ---- d.2
#
# b.1 ---- c.2
#
# If we downgrade module d to version 1, we must downgrade b as well.
# If that downgrade selects b version 1, we will upgrade module c to version 2.

cp go.mod go.mod.orig
go mod tidy
cmp go.mod.orig go.mod

# Downgrading d to version 1 downgrades b, which upgrades c.
go get -v example.com/d@v0.1.0
go list -m all
stdout '^example.com/b v0.1.0 '

		}
	}

	// 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)

To add missing module requirements or remove unneeded requirements,
use 'go mod tidy'. For details, see 'go help mod tidy' or
https://golang.org/ref/mod#go-mod-tidy.

To add, upgrade, downgrade, or remove a specific module requirement, use
'go get'. For details, see 'go help module-get' or
https://golang.org/ref/mod#go-get.

To make other changes or to parse go.mod as JSON for use by other tools,

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)

go list -m -u all
stdout '^example.com/pseudoupgrade v0.1.1-0.20190429073117-b5426c86b553$'

# 'get -u' should not downgrade to the (lower) tagged version.
go get -u
go list -m -u all
stdout '^example.com/pseudoupgrade v0.1.1-0.20190429073117-b5426c86b553$'

# 'get example.com/pseudoupgrade@upgrade' should not downgrade.
go get example.com/pseudoupgrade@upgrade
go list -m all

example.com/downgrade/v2 v2.0.1
written by hand

-- .mod --
module example.com/downgrade/v2

require rsc.io/quote v1.5.2
-- .info --
{"Version":"v2.0.1"}
-- go.mod --
module example.com/downgrade/v2

example.com/downgrade v2.0.0
written by hand

-- .mod --
module example.com/downgrade

require rsc.io/quote v1.5.2
-- .info --

#
# a ---- b ---- d
#
# The module dependency graph originally looks like:
#
# a ---- b.2 ---- d.2
#
# b.1 ---- c.1
#
# If we downgrade module d to version 1, we must downgrade b as well.
# If that downgrade selects b version 1, we will add a new dependency on module c.

cp go.mod go.mod.orig
go mod tidy
cmp go.mod.orig go.mod

go get example.com/d@v0.1.0
go list -m all

go mod edit -require example.com/retract/self/prev@v1.1.0
go get example.com/retract/self/prev
go list -m example.com/retract/self/prev
stdout '^example.com/retract/self/prev v1.1.0$'

# 'go get pkg' should not downgrade from a retracted version when no higher
# version is available.
cp go.mod.orig go.mod
go mod edit -require example.com/retract/self/prev@v1.9.0
go get example.com/retract/self/prev

)

var (
	migrateCmd = &cobra.Command{
		Short: "Upgrade/downgrade etcd data across multiple versions",
		Long: `Upgrade or downgrade etcd data across multiple versions to the target version

Given a 'bin-dir' directory of etcd and etcdctl binaries, an etcd 'data-dir' with a 'version.txt' file and
a target etcd version, this tool will upgrade or downgrade the etcd data from the version specified in
'version.txt' to the target version.