Add --no-headers flag to tkn eventlistener list command

docs/cmd/tkn_eventlistener_list.md

@@ -31,6 +31,7 @@ or
   -A, --all-namespaces                list EventListeners from all namespaces
       --allow-missing-template-keys   If true, ignore any errors in templates when a field or map key is missing in the template. Only applies to golang and jsonpath output formats. (default true)
   -h, --help                          help for list
+      --no-headers                    do not print column headers with output (default print column headers with output)
   -o, --output string                 Output format. One of: json|yaml|name|go-template|go-template-file|template|templatefile|jsonpath|jsonpath-file.
       --template string               Template string or path to template file to use when -o=go-template, -o=go-template-file. The template format is golang templates [http://golang.org/pkg/text/template/#pkg-overview].
 ```

docs/man/man1/tkn-eventlistener-list.1

@@ -31,6 +31,10 @@ Lists EventListeners in a namespace
 \fB\-h\fP, \fB\-\-help\fP[=false]
     help for list
 
+.PP
+\fB\-\-no\-headers\fP[=false]
+    do not print column headers with output (default print column headers with output)
+
 .PP
 \fB\-o\fP, \fB\-\-output\fP=""
     Output format. One of: json|yaml|name|go\-template|go\-template\-file|template|templatefile|jsonpath|jsonpath\-file.

pkg/cmd/eventlistener/list.go

@@ -38,6 +38,7 @@ const (
 
 type listOptions struct {
 	AllNamespaces bool
+	NoHeaders     bool
 }
 
 func listCommand(p cli.Params) *cobra.Command {
@@ -94,7 +95,7 @@ or
 				return printer.PrintObject(stream.Out, els, f)
 			}
 
-			if err = printFormatted(stream, els, p, opts.AllNamespaces); err != nil {
+			if err = printFormatted(stream, els, p, opts.AllNamespaces, opts.NoHeaders); err != nil {
 				return errors.New(`failed to print EventListeners`)
 			}
 			return nil
@@ -103,6 +104,7 @@ or
 
 	f.AddFlags(c)
 	c.Flags().BoolVarP(&opts.AllNamespaces, "all-namespaces", "A", opts.AllNamespaces, "list EventListeners from all namespaces")
+	c.Flags().BoolVar(&opts.NoHeaders, "no-headers", opts.NoHeaders, "do not print column headers with output (default print column headers with output)")
 	return c
 }
 
@@ -123,7 +125,7 @@ func list(client versioned.Interface, namespace string) (*v1alpha1.EventListener
 	return els, nil
 }
 
-func printFormatted(s *cli.Stream, els *v1alpha1.EventListenerList, p cli.Params, allNamespaces bool) error {
+func printFormatted(s *cli.Stream, els *v1alpha1.EventListenerList, p cli.Params, allNamespaces bool, noHeaders bool) error {
 	if len(els.Items) == 0 {
 		fmt.Fprintln(s.Err, emptyMsg)
 		return nil
@@ -135,7 +137,9 @@ func printFormatted(s *cli.Stream, els *v1alpha1.EventListenerList, p cli.Params
 	}
 
 	w := tabwriter.NewWriter(s.Out, 0, 5, 3, ' ', tabwriter.TabIndent)
-	fmt.Fprintln(w, headers)
+	if !noHeaders {
+		fmt.Fprintln(w, headers)
+	}
 	for _, el := range els.Items {
 
 		status := corev1.ConditionStatus("---")

pkg/cmd/eventlistener/list_test.go

@@ -104,6 +104,18 @@ func TestListEventListener(t *testing.T) {
 			args:      []string{"list", "--all-namespaces"},
 			wantError: false,
 		},
+		{
+			name:      "List EventListeners without headers",
+			command:   command(t, els, now, ns),
+			args:      []string{"list", "--no-headers"},
+			wantError: false,
+		},
+		{
+			name:      "List EventListeners from all namespaces without headers",
+			command:   command(t, els, now, ns),
+			args:      []string{"list", "--no-headers", "--all-namespaces"},
+			wantError: false,
+		},
 	}
 
 	for _, td := range tests {

pkg/cmd/eventlistener/testdata/TestListEventListener-List_EventListeners_from_all_namespaces_without_headers.golden

@@ -0,0 +1,6 @@
+bar   tb0   2 minutes ago    http://tb0-listener.default.svc.cluster.local   True
+foo   tb1   2 minutes ago    http://tb1-listener.default.svc.cluster.local   True
+foo   tb2   30 seconds ago   http://tb2-listener.default.svc.cluster.local   True
+foo   tb3   1 week ago       http://tb3-listener.default.svc.cluster.local   True
+foo   tb4   ---              ---                                             ---
+foo   tb5   10 seconds ago   ---                                             False

pkg/cmd/eventlistener/testdata/TestListEventListener-List_EventListeners_without_headers.golden

@@ -0,0 +1,6 @@
+tb0   2 minutes ago    http://tb0-listener.default.svc.cluster.local   True
+tb1   2 minutes ago    http://tb1-listener.default.svc.cluster.local   True
+tb2   30 seconds ago   http://tb2-listener.default.svc.cluster.local   True
+tb3   1 week ago       http://tb3-listener.default.svc.cluster.local   True
+tb4   ---              ---                                             ---
+tb5   10 seconds ago   ---                                             False