enable to filter command in help command

bundlebee-core/src/main/java/io/yupiik/bundlebee/core/command/impl/HelpCommand.java

@@ -47,6 +47,11 @@ public class HelpCommand implements Executable {
     @Inject
     private BeanManager beanManager;
 
+    @Inject
+    @Description("Which command to show help for.")
+    @ConfigProperty(name = "bundlebee.help.command", defaultValue = "")
+    private String command;
+
     @Override
     public String name() {
         return "help";
@@ -65,6 +70,7 @@ public CompletionStage<?> execute() {
                 "  BundleBee is a light Kubernetes package manager. Available commands:\n" +
                 "\n" +
                 stream(executables)
+                        .filter(it -> command.isBlank() || command.equals(it.name()))
                         .map(executable -> {
                             final var parameters = findParameters(executable).collect(toList());
                             final var desc = reflowText(executable.description()

bundlebee-core/src/test/java/io/yupiik/bundlebee/core/command/impl/HelpCommandTest.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2021 - Yupiik SAS - https://www.yupiik.com
+ * 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
+ *
+ *  http://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 io.yupiik.bundlebee.core.command.impl;
+
+import io.yupiik.bundlebee.core.BundleBee;
+import io.yupiik.bundlebee.core.test.BundleBeeExtension;
+import io.yupiik.bundlebee.core.test.CommandExecutor;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+import static java.util.logging.Level.INFO;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class HelpCommandTest { // BundleBeeTest already test help command (since it is always there)
+    @RegisterExtension
+    BundleBeeExtension extension = new BundleBeeExtension();
+
+    @Test
+    void helpOneCommand(final CommandExecutor executor) {
+        final var logs = executor.wrap(INFO, () -> new BundleBee().launch("help", "--command", "version"));
+        assertEquals("" +
+                "\n" +
+                "BundleBee\n" +
+                "\n" +
+                "  BundleBee is a light Kubernetes package manager. Available commands:\n" +
+                "\n" +
+                "  [] version: shows the application version.\n" +
+                "\n" +
+                "\n" +
+                "", logs);
+    }
+}