Mark --inject-broker flag as deprecated (#1665)

Co-authored-by: David Simansky <dsimansk@redhat.com>

docs/cmd/kn_trigger_create.md

@@ -23,7 +23,6 @@ kn trigger create NAME --sink SINK
       --broker string      Name of the Broker which the trigger associates with. (default "default")
       --filter strings     Key-value pair for exact CloudEvent attribute matching against incoming events, e.g type=dev.knative.foo
   -h, --help               help for create
-      --inject-broker      Create new broker with name default through common annotation
   -n, --namespace string   Specify the namespace to operate in.
   -s, --sink string        Addressable sink for events. You can specify a broker, channel, Knative service or URI. Examples: '--sink broker:nest' for a broker 'nest', '--sink channel:pipe' for a channel 'pipe', '--sink ksvc:mysvc:mynamespace' for a Knative service 'mysvc' in another namespace 'mynamespace', '--sink https://event.receiver.uri' for an URI with an 'http://' or 'https://' schema, '--sink ksvc:receiver' or simply '--sink receiver' for a Knative service 'receiver' in the current namespace. If a prefix is not provided, it is considered as a Knative service in the current namespace. If referring to a Knative service in another namespace, 'ksvc:name:namespace' combination must be provided explicitly.
 ```

docs/cmd/kn_trigger_update.md

@@ -27,7 +27,6 @@ kn trigger update NAME
       --broker string      Name of the Broker which the trigger associates with. (default "default")
       --filter strings     Key-value pair for exact CloudEvent attribute matching against incoming events, e.g type=dev.knative.foo
   -h, --help               help for update
-      --inject-broker      Create new broker with name default through common annotation
   -n, --namespace string   Specify the namespace to operate in.
   -s, --sink string        Addressable sink for events. You can specify a broker, channel, Knative service or URI. Examples: '--sink broker:nest' for a broker 'nest', '--sink channel:pipe' for a channel 'pipe', '--sink ksvc:mysvc:mynamespace' for a Knative service 'mysvc' in another namespace 'mynamespace', '--sink https://event.receiver.uri' for an URI with an 'http://' or 'https://' schema, '--sink ksvc:receiver' or simply '--sink receiver' for a Knative service 'receiver' in the current namespace. If a prefix is not provided, it is considered as a Knative service in the current namespace. If referring to a Knative service in another namespace, 'ksvc:name:namespace' combination must be provided explicitly.
 ```

pkg/kn/commands/trigger/update_flags.go

@@ -51,6 +51,12 @@ func (f *TriggerUpdateFlags) GetUpdateFilters() (map[string]string, []string, er
 //Add is to set parameters
 func (f *TriggerUpdateFlags) Add(cmd *cobra.Command) {
 	cmd.Flags().StringVar(&f.Broker, "broker", "default", "Name of the Broker which the trigger associates with.")
+	// The Sugar controller was integrated into main Eventing controller. With that the default behavior was changed as well.
+	// Users need to configure 'Automatic Broker Creation' per linked docs.
+	// Deprecated in 1.4, remove in 1.6.
 	cmd.Flags().BoolVar(&f.InjectBroker, "inject-broker", false, "Create new broker with name default through common annotation")
+	cmd.Flags().MarkDeprecated("inject-broker", "effective since 1.4 and will be removed in 1.6 release. \n"+
+		"Please refer to 'Automatic Broker Creation' section for configuration options, "+
+		"https://knative.dev/docs/eventing/sugar/#automatic-broker-creation.")
 	cmd.Flags().StringSliceVar(&f.Filters, "filter", nil, "Key-value pair for exact CloudEvent attribute matching against incoming events, e.g type=dev.knative.foo")
 }