Added a //help command.

src/main/java/com/sk89q/minecraft/util/commands/CommandsManager.java

@@ -87,6 +87,12 @@ public abstract class CommandsManager<T> {
      */
     protected Injector injector;
 
+    /**
+     * Mapping of commands (not including aliases) with a description. This
+     * is only for top level commands.
+     */
+    protected Map<String, String> helpMessages = new HashMap<String, String>();
+
     /**
      * Register an class that contains commands (denoted by {@link Command}.
      * If no dependency injector is specified, then the methods of the
@@ -189,11 +195,32 @@ public abstract class CommandsManager<T> {
             // Build a list of commands and their usage details, at least for
             // root level commands
             if (parent == null) {
-                if (cmd.usage().length() == 0) {
-                    descs.put(cmd.aliases()[0], cmd.desc());
+                final String commandName = cmd.aliases()[0];
+                final String desc = cmd.desc();
+
+                final String usage = cmd.usage();
+                if (usage.length() == 0) {
+                    descs.put(commandName, desc);
                 } else {
-                    descs.put(cmd.aliases()[0], cmd.usage() + " - " + cmd.desc());
+                    descs.put(commandName, usage + " - " + desc);
                 }
+
+                String help = cmd.help();
+                if (help.length() == 0) {
+                    help = desc;
+                }                     
+
+                final CharSequence arguments = getArguments(cmd);
+                for (String alias : cmd.aliases()) {
+                    final String helpMessage = "/"+alias+" "+arguments+"\n\n"+help;
+                    final String key = alias.replaceAll("/", "");
+                    String previous = helpMessages.put(key, helpMessage);
+
+                    if (previous != null && !previous.replaceAll("^/[^ ]+ ", "").equals(helpMessage.replaceAll("^/[^ ]+ ", ""))) {
+                        helpMessages.put(key, previous+"\n\n"+helpMessage);
+                    }
+                }
+
             }
 
             // Add the command to the registered command list for return
@@ -233,6 +260,15 @@ public abstract class CommandsManager<T> {
         return descs;
     }
 
+    /**
+     * Get a map from command name to help message. This is only for root commands.
+     * 
+     * @return
+     */
+    public Map<String, String> getHelpMessages() {
+        return helpMessages;
+    }
+
     /**
      * Get the usage string for a command.
      * 
@@ -250,17 +286,7 @@ public abstract class CommandsManager<T> {
             command.append(args[i]);
             command.append(' ');
         }
-        if (cmd.flags().length() > 0) {
-            String flags = cmd.flags().replaceAll(".:", "");
-            if (flags.length() > 0) {
-                command.append("[-");
-                for (int i = 0; i < flags.length(); ++i) {
-                    command.append(flags.charAt(i));
-                }
-                command.append("] ");
-            }
-        }
-        command.append(cmd.usage());
+        command.append(getArguments(cmd));
 
         final String help = cmd.help();
         if (!help.isEmpty()) {
@@ -271,6 +297,26 @@ public abstract class CommandsManager<T> {
         return command.toString();
     }
 
+    protected CharSequence getArguments(Command cmd) {
+        final String flags = cmd.flags();
+
+        final StringBuilder command2 = new StringBuilder();
+        if (flags.length() > 0) {
+            String flagString = flags.replaceAll(".:", "");
+            if (flagString.length() > 0) {
+                command2.append("[-");
+                for (int i = 0; i < flagString.length(); ++i) {
+                    command2.append(flagString.charAt(i));
+                }
+                command2.append("] ");
+            }
+        }
+
+        command2.append(cmd.usage());
+
+        return command2;
+    }
+
     /**
      * Get the usage string for a nested command.
      * 

src/main/java/com/sk89q/worldedit/WorldEdit.java

@@ -983,6 +983,13 @@ public class WorldEdit {
         return commands.getCommands();
     }
 
+    /**
+     * @return the commands
+     */
+    public CommandsManager<LocalPlayer> getCommandsManager() {
+        return commands;
+    }
+
     /**
      *
      * @param player

src/main/java/com/sk89q/worldedit/commands/UtilityCommands.java

@@ -20,9 +20,13 @@
 package com.sk89q.worldedit.commands;
 
 import java.util.Set;
+import java.util.SortedSet;
+import java.util.TreeSet;
+
 import com.sk89q.minecraft.util.commands.Command;
 import com.sk89q.minecraft.util.commands.CommandContext;
 import com.sk89q.minecraft.util.commands.CommandPermissions;
+import com.sk89q.minecraft.util.commands.CommandsManager;
 import com.sk89q.minecraft.util.commands.Logging;
 import static com.sk89q.minecraft.util.commands.Logging.LogMode.*;
 import com.sk89q.worldedit.*;
@@ -426,4 +430,48 @@ public class UtilityCommands {
         int removed = player.getWorld().removeEntities(type, origin, radius);
         player.print("Marked " + removed + " entit(ies) for removal.");
     }
+
+    @Command(
+        aliases = { "/help" },
+        usage = "[<command>]",
+        desc = "Displays help for the given command or lists all commands.",
+        min = 0,
+        max = -1
+    )
+    public static void help(CommandContext args, WorldEdit we,
+            LocalSession session, LocalPlayer player, EditSession editSession)
+            throws WorldEditException {
+
+        final CommandsManager<LocalPlayer> commandsManager = we.getCommandsManager();
+
+        if (args.argsLength() == 0) {
+            StringBuilder sb = new StringBuilder();
+            boolean first = true;
+            SortedSet<String> commands = new TreeSet<String>(commandsManager.getCommands().keySet());
+
+            for (String command : commands) {
+                if (!first) {
+                    sb.append(", ");
+                }
+
+                sb.append('/');
+                sb.append(command);
+                first = false;
+            }
+
+            player.print(sb.toString());
+
+            return;
+        }
+
+        String command = args.getJoinedStrings(0).replaceAll("/", "");
+
+        String helpMessage = commandsManager.getHelpMessages().get(command);
+        if (helpMessage == null) {
+            player.printError("Unknown command '" + command + "'.");
+            return;
+        }
+
+        player.print(helpMessage);
+    }
 }