Implement command (no arg)

https://redis.io/docs/latest/commands/command/

Adding it for completeness and as alternative to COMMAND INFO for Redis server prior 7.0.0.

COMMAND (no args) is available with Redis 2.x
COMMAND INFO is available since REDIS version 7.0.0

Relates to: #2922
Support COMMAND commands (#2922)
commit  : 3590438

Closes #793

src/main/java/redis/clients/jedis/Jedis.java

@@ -8253,6 +8253,12 @@ public Map<String, CommandInfo> commandInfo(String... commands) {
     return CommandInfo.COMMAND_INFO_RESPONSE.build(connection.getOne());
   }
 
+  public Map<String, CommandInfo> command() {
+    checkIsInMultiOrPipeline();
+    connection.sendCommand(COMMAND);
+    return CommandInfo.COMMAND_INFO_RESPONSE.build(connection.getOne());
+  }
+
   public List<String> commandList() {
     checkIsInMultiOrPipeline();
     connection.sendCommand(COMMAND, LIST);

src/test/java/redis/clients/jedis/commands/jedis/ControlCommandsTest.java

@@ -21,6 +21,7 @@
 import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
 
+import com.google.gson.annotations.Since;
 import org.hamcrest.MatcherAssert;
 import org.hamcrest.Matchers;
 import org.junit.Test;
@@ -501,6 +502,28 @@ public void commandGetKeys() {
     assertEquals(2, keySandFlags.get(0).getValue().size());
   }
 
+
+  @Test
+  public void command() {
+    Map<String, CommandInfo> infos = jedis.command();
+
+    assertThat(infos.size(),greaterThan(0));
+
+    CommandInfo getInfo = infos.get("get");
+    assertEquals(2, getInfo.getArity());
+    assertEquals(2, getInfo.getFlags().size());
+    assertEquals(1, getInfo.getFirstKey());
+    assertEquals(1, getInfo.getLastKey());
+    assertEquals(1, getInfo.getStep());
+
+    assertNull(infos.get("foo")); // non-existing command
+
+    CommandInfo setInfo = infos.get("set");
+    assertEquals(3, setInfo.getAclCategories().size());
+    assertEquals(0, setInfo.getTips().size());
+    assertEquals(0, setInfo.getSubcommands().size());
+  }
+
   @Test
   public void commandInfo() {
     Map<String, CommandInfo> infos = jedis.commandInfo("GET", "foo", "SET");