cli-plugins/manager: add IsPluginCommand(() utility

This makes it more convenient to check if a command is a plugin-stub

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli-plugins/manager/manager.go

@@ -224,3 +224,8 @@ func PluginRunCommand(dockerCli command.Cli, name string, rootcmd *cobra.Command
 	}
 	return nil, errPluginNotFound(name)
 }
+
+// IsPluginCommand checks if the given cmd is a plugin-stub.
+func IsPluginCommand(cmd *cobra.Command) bool {
+	return cmd.Annotations[CommandAnnotationPlugin] == "true"
+}

cli-plugins/manager/plugin.go

@@ -69,7 +69,7 @@ func newPlugin(c Candidate, rootcmd *cobra.Command) (Plugin, error) {
 			// Ignore conflicts with commands which are
 			// just plugin stubs (i.e. from a previous
 			// call to AddPluginCommandStubs).
-			if p := cmd.Annotations[CommandAnnotationPlugin]; p == "true" {
+			if IsPluginCommand(cmd) {
 				continue
 			}
 			if cmd.Name() == p.Name {