Fix alias handling with @Command annotation

- Revisit how alias commands are added using
  @Command annotation when using if/or on class
  and/or method level.
- With this change alias handling is more logical
  and there's better tests and docs.
- Backport #945
- Fixes #973

spring-shell-docs/src/test/java/org/springframework/shell/docs/CommandRegistrationAliasSnippets.java

@@ -0,0 +1,107 @@
+/*
+ * Copyright 2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.shell.docs;
+
+import org.springframework.shell.command.CommandRegistration;
+import org.springframework.shell.command.annotation.Command;
+
+class CommandRegistrationAliasSnippets {
+
+	// tag::builder[]
+	CommandRegistration commandRegistration() {
+		return CommandRegistration.builder()
+			.command("mycommand")
+			// define alias as myalias
+			.withAlias()
+				.command("myalias")
+				.and()
+			// define alias as myalias1 and myalias2
+			.withAlias()
+				.command("myalias1", "myalias2")
+				.and()
+			.build();
+	}
+	// end::builder[]
+
+	class Dump1 {
+
+		// tag::command1[]
+		@Command
+		class MyCommands {
+
+			@Command(command = "mycommand", alias = "myalias")
+			void myCommand() {
+			}
+		}
+		// end::command1[]
+	}
+
+	class Dump2 {
+
+		// tag::command2[]
+		@Command
+		class MyCommands {
+
+			@Command(command = "mycommand", alias = { "myalias1", "myalias2" })
+			void myCommand() {
+			}
+		}
+		// end::command2[]
+	}
+
+	class Dump3 {
+
+		// tag::command3[]
+		@Command(alias = "myalias")
+		class MyCommands {
+
+			@Command(command = "mycommand")
+			void myCommand() {
+			}
+		}
+		// end::command3[]
+	}
+
+	class Dump4 {
+
+		// tag::command4[]
+		@Command(alias = "myalias1")
+		class MyCommands {
+
+			@Command(command = "mycommand", alias = "myalias2")
+			void myCommand() {
+			}
+		}
+		// end::command4[]
+	}
+
+	class Dump5 {
+
+		// tag::command5[]
+		@Command(command = "mycommand", alias = "myalias")
+		class MyCommands {
+
+			@Command(command = "", alias = "")
+			void myMainCommand() {
+			}
+
+			@Command(command = "mysubcommand", alias = "mysubalias")
+			void mySubCommand() {
+			}
+		}
+		// end::command5[]
+	}
+}