Support label with @Option

- Add `label` field into `@Option`. This sets option label if
  `label` field has any text.
- Fixes #732

spring-shell-core/src/main/java/org/springframework/shell/command/annotation/Option.java

@@ -70,6 +70,13 @@ public @interface Option {
 	 */
 	String description() default "";
 
+	/**
+	 * Return a label of the option.
+	 *
+	 * @return label of the option
+	 */
+	String label() default "";
+
 	/**
 	 * Define option arity.
 	 *

spring-shell-core/src/main/java/org/springframework/shell/command/annotation/support/CommandRegistrationFactoryBean.java

@@ -251,6 +251,9 @@ class CommandRegistrationFactoryBean implements FactoryBean<CommandRegistration>
 				optionSpec.shortNames(shortNames.toArray(new Character[0]));
 				optionSpec.position(mp.getParameterIndex());
 				optionSpec.description(so.description());
+				if (StringUtils.hasText(so.label())) {
+					optionSpec.label(so.label());
+				}
 				int arityMin = so.arityMin();
 				int arityMax = so.arityMax();
 				if (arityMin > -1) {

spring-shell-core/src/test/java/org/springframework/shell/command/annotation/support/CommandRegistrationFactoryBeanTests.java

@@ -305,14 +305,27 @@ class CommandRegistrationFactoryBeanTests {
 		@Command
 		void command4(@Option(longNames = "arg", arityMax = 2, arity = OptionArity.EXACTLY_ONE) String arg) {
 		}
+	}
 
-		@Bean
-		CompletionProvider completionProvider() {
-			return ctx -> {
-				return Collections.emptyList();
-			};
+	@Test
+	void setsOptionWithLabel() {
+		configCommon(OptionWithLabel.class, new OptionWithLabel(), "command1", new Class[] { String.class })
+				.run((context) -> {
+					CommandRegistrationFactoryBean fb = context.getBean(FACTORYBEANREF,
+							CommandRegistrationFactoryBean.class);
+					assertThat(fb).isNotNull();
+					CommandRegistration registration = fb.getObject();
+					assertThat(registration).isNotNull();
+					assertThat(registration.getOptions().get(0).getLabel()).isEqualTo("label");
+		});
+	}
+
+	@Command
+	private static class OptionWithLabel {
+
+		@Command
+		void command1(@Option(longNames = "arg", label = "label") String arg) {
 		}
-
 	}
 
 	private <T> ApplicationContextRunner configCommon(Class<T> type, T bean) {