Remove uses of "--" as constant prefix

Code now uses the prefixForMethod(...)
added sample usage of prefix in a @ShellMethod

spring-shell2-samples/src/main/java/org/springframework/shell2/samples/standard/Commands.java

@@ -44,8 +44,13 @@ public class Commands {
 	}
 
 	@ShellMethod(help = "it's cool")
-	public void foo(String bar) {
-
+	public String foo(String bar) {
+		return bar;
+	}
+	
+	@ShellMethod(help = "it's cool with a prefix", prefix = "-")
+	public String fooPrefix(String bar) {
+		return bar;
 	}
 
 	@ShellMethod(help = "Shows support for boolean parameters, with arity=0")

spring-shell2-standard/src/main/java/org/springframework/shell2/standard/StandardParameterResolver.java

@@ -105,7 +105,7 @@ public class StandardParameterResolver implements ParameterResolver {
 
 	@Override
 	public Object resolve(MethodParameter methodParameter, List<String> words) {
-		String prefix = prefixForMethod(methodParameter);
+		String prefix = prefixForMethod(methodParameter.getMethod());
 
 		CacheKey cacheKey = new CacheKey(methodParameter.getMethod(), words);
 		Map<Parameter, ParameterRawValue> resolved = parameterCache.computeIfAbsent(cacheKey, (k) -> {
@@ -195,7 +195,7 @@ public class StandardParameterResolver implements ParameterResolver {
 	}
 
 	private Set<String> gatherAllPossibleKeys(Method method) {
-		final String prefix = "--";
+		final String prefix = prefixForMethod(method);
 		return Arrays.stream(method.getParameters())
 				.flatMap(p -> {
 					ShellOption option = p.getAnnotation(ShellOption.class);
@@ -208,8 +208,8 @@ public class StandardParameterResolver implements ParameterResolver {
 				}).collect(Collectors.toSet());
 	}
 
-	private String prefixForMethod(MethodParameter methodParameter) {
-		return methodParameter.getMethod().getAnnotation(ShellMethod.class).prefix();
+	private String prefixForMethod(Method method) {
+		return method.getAnnotation(ShellMethod.class).prefix();
 	}
 
 	private Optional<String> defaultValueFor(Parameter parameter) {
@@ -380,7 +380,7 @@ public class StandardParameterResolver implements ParameterResolver {
 	 * or from the actual parameter name.
 	 */
 	private Stream<String> getKeysForParameter(Method method, int index) {
-		String prefix = "--";
+		String prefix = prefixForMethod(method);
 		Parameter p = method.getParameters()[index];
 		ShellOption option = p.getAnnotation(ShellOption.class);
 		if (option != null && option.value().length > 0) {

spring-shell2-standard/src/test/java/org/springframework/shell2/standard/Remote.java

@@ -45,12 +45,16 @@ public class Remote {
 	                String name,
 	                @ShellOption(defaultValue="defoolt") String foo,
 	                @ShellOption(value = {"--bar", "--baz"}, defaultValue = "last") String bar) {
-
 	}
 
 	@ShellMethod(help = "bye bye")
 	public void shutdown(@ShellOption Delay delay) {
 
+	}
+	
+	@ShellMethod(help = "a different prefix", prefix = "-")
+	public void prefixTest(@ShellOption String message) {
+
 	}
 
 	@ShellMethod(help = "add 3 numbers together")

spring-shell2-standard/src/test/java/org/springframework/shell2/standard/StandardParameterResolverTest.java

@@ -74,6 +74,16 @@ public class StandardParameterResolverTest {
 		)).isEqualTo("last");
 
 	}
+	
+	@Test
+	public void testParsesWithMethodPrefix() throws Exception {
+		Method method = findMethod(Remote.class, "prefixTest", String.class);
+
+		assertThat(resolver.resolve(
+				Utils.createMethodParameter(method, 0),
+				asList("-message abc".split(" "))
+		)).isEqualTo("abc");
+	}
 
 	@Test
 	public void testParameterSpecifiedTwiceViaDifferentAliases() throws Exception {