Provide option to hide default 'completion' cmd (spf13#1541)

Fixes spf13#1507

Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>

completions.go

@@ -93,6 +93,8 @@ type CompletionOptions struct {
 	// DisableDescriptions turns off all completion descriptions for shells
 	// that support them
 	DisableDescriptions bool
+	// HiddenDefaultCmd makes the default 'completion' command hidden
+	HiddenDefaultCmd bool
 }
 
 // NoFileCompletions can be used to disable file completion for commands that should
@@ -605,6 +607,7 @@ See each sub-command's help for details on how to use the generated script.
 `, c.Root().Name()),
 		Args:              NoArgs,
 		ValidArgsFunction: NoFileCompletions,
+		Hidden:            c.CompletionOptions.HiddenDefaultCmd,
 	}
 	c.AddCommand(completionCmd)
 

completions_test.go

@@ -2398,6 +2398,21 @@ func TestDefaultCompletionCmd(t *testing.T) {
 	rootCmd.CompletionOptions.DisableDescriptions = false
 	// Remove completion command for the next test
 	removeCompCmd(rootCmd)
+
+	// Test that the 'completion' command can be hidden
+	rootCmd.CompletionOptions.HiddenDefaultCmd = true
+	assertNoErr(t, rootCmd.Execute())
+	compCmd, _, err = rootCmd.Find([]string{compCmdName})
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+	if compCmd.Hidden == false {
+		t.Error("Default 'completion' command should be hidden but it is not")
+	}
+	// Re-enable for next test
+	rootCmd.CompletionOptions.HiddenDefaultCmd = false
+	// Remove completion command for the next test
+	removeCompCmd(rootCmd)
 }
 
 func TestCompleteCompletion(t *testing.T) {