// Compatibility determines whether we should transparently deploy echo workloads attached to each revision
	// specified in `Revisions` when creating echo instances. Used primarily for compatibility testing between revisions
	// on different control plane versions.
	Compatibility bool

	// Revisions maps the Istio revisions that are available to each cluster to their corresponding versions.

apiVersion: release-notes/v2
kind: bug-fix
area: istioctl
releaseNotes:
  - |

  # Defines the mapping from revision tags to revisions.
  #
  # The following fields can be set for each revision tag:
  #   (1) revision (REQUIRED): the revision to use for this revision tag.
  #   (2) namespace: the namespace containing the istiod revision.
  #   (3) validationURL: the URL to use for validation on this revision tag.
  #   (4) injectionURL: the URL to for injection on this revision tag.

	}

	// If the user is performing purge but also specified a revision, we should warn
	// that the purge will still remove all resources
	if orArgs.purge && orArgs.revision != "" {
		orArgs.revision = ""
		l.LogAndPrint("Purge remove will remove all Istio operator controller, ignoring the specified revision\n")
	}

	var installed bool
	if orArgs.revision == "default" {

Davanum Srinivas <******@****.***> 1652185809 -0400

						return fmt.Errorf("validatingwebhookconfiguration not updated yet: %v", err)
					}
					return nil
				})
			}

			revision := "default"
			if t.Settings().Revisions.Default() != "" {
				revision = t.Settings().Revisions.Default()
			}
			verifyRejectsInvalidConfig(t, revision, true)
			verifyRejectsInvalidConfig(t, "", true)
		})
}

	whs.Create(makeTag("revision", "tag-foo"))
	track.WaitOrdered("revision,tag-foo")
	assert.Equal(t, tw.GetMyTags(), sets.New("revision", "tag-foo"))

	whs.Create(makeTag("revision", "tag-bar"))
	track.WaitOrdered("revision,tag-bar,tag-foo")
	assert.Equal(t, tw.GetMyTags(), sets.New("revision", "tag-foo", "tag-bar"))

	whs.Update(makeTag("not-revision", "tag-bar"))
	track.WaitOrdered("revision,tag-foo")

func (c *Config) overwriteRevisionIfEmpty(revision string) {
	// Overwrite the default namespace label (istio-injection=enabled)
	// with istio.io/rev=XXX. If a revision label is already provided,
	// the label will remain as is.
	if c.Revision == "" {
		c.Revision = revision
	}
	// Allow setting revision explicitly to `default` to avoid configuration overwrite
	if c.Revision == "default" {
		c.Revision = ""
	}
}

// when the default revision changes.
type DefaultWatcher interface {
	Run(stopCh <-chan struct{})
	HasSynced() bool
	GetDefault() string
	AddHandler(handler DefaultHandler)
}

// DefaultHandler is a callback for when the default revision changes.
type DefaultHandler func(string)

type defaultWatcher struct {
	revision        string
	defaultRevision string
	handlers        []DefaultHandler

## Upgrade Planning