Restore default name of command groups as in v3

This commit restores the default name of command groups
as in v3. Utils.splitCamelCase copied verbatim from v3.

Resolves #1308

Author: fmbenhassine

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

@@ -82,7 +82,16 @@ public Command getObject() {
 		description = description.isEmpty() ? "N/A" : description;
 		String help = command.help();
 		String group = command.group();
-		group = group.isEmpty() ? this.method.getDeclaringClass().getSimpleName() + " Commands" : group;
+		if (group.isEmpty()) {
+			String simpleName = Utils.splitCamelCase(this.method.getDeclaringClass().getSimpleName());
+			if (!simpleName.endsWith(" Commands")) {
+				group = simpleName + " Commands";
+			}
+			else {
+				group = simpleName;
+			}
+
+		}
 		boolean hidden = command.hidden();
 		String[] aliases = command.alias();
 		String availabilityProviderBeanName = command.availabilityProvider();

spring-shell-core/src/main/java/org/springframework/shell/core/utils/Utils.java

@@ -30,6 +30,7 @@
 import org.springframework.shell.core.command.CommandRegistry;
 import org.springframework.shell.core.command.ExitStatus;
 import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
 
 /**
  * Some text utilities.
@@ -39,6 +40,17 @@
  */
 public class Utils {
 
+	/**
+	 * Split a CamelCase class name into separate words. Used to derive command group
+	 * names. For example, "MyCommands" becomes "My Commands".
+	 * @param className the simple class name
+	 * @return the split string
+	 */
+	public static String splitCamelCase(String className) {
+		String[] tokens = className.split("(?<=[a-z])(?=[A-Z])|(?<=[A-Z])(?=[A-Z][a-z])");
+		return StringUtils.arrayToDelimitedString(tokens, " ");
+	}
+
 	/**
 	 * Turn CamelCaseText into gnu-style-lowercase.
 	 */

spring-shell-core/src/test/java/org/springframework/shell/core/UtilsTests.java

@@ -33,6 +33,12 @@
  */
 class UtilsTests {
 
+	@Test
+	void testSplitCamelCase() {
+		assertThat(Utils.splitCamelCase("MyCommands")).isEqualTo("My Commands");
+		assertThat(Utils.splitCamelCase("MyAppCommands")).isEqualTo("My App Commands");
+	}
+
 	@Test
 	public void testUnCamelify() throws Exception {
 		assertThat(Utils.unCamelify("HelloWorld")).isEqualTo("hello-world");