Added registration of plugin commands on plugin load.

src/main/java/net/minecraft/server/NetServerHandler.java

@@ -18,6 +18,7 @@ import org.bukkit.event.block.BlockRightClickEvent;
 import org.bukkit.event.player.PlayerChatEvent;
 import org.bukkit.event.player.PlayerItemEvent;
 import org.bukkit.event.player.PlayerMoveEvent;
+import org.bukkit.plugin.Plugin;
 // CraftBukkit end
 
 public class NetServerHandler extends NetHandler implements ICommandListener {
@@ -536,6 +537,11 @@ public class NetServerHandler extends NetHandler implements ICommandListener {
 
     private void c(String s) {
         // CraftBukkit start
+        boolean targetPluginFound = server.dispatchCommand(player, s);
+        if (targetPluginFound) {
+            return;
+        }
+        
         PlayerChatEvent event = new PlayerChatEvent(Type.PLAYER_COMMAND, player, s);
         server.getPluginManager().callEvent(event);
         if (event.isCancelled()) {

src/main/java/org/bukkit/craftbukkit/CraftServer.java

@@ -10,8 +10,10 @@ import net.minecraft.server.EntityPlayerMP;
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.ServerConfigurationManager;
 import org.bukkit.*;
+import org.bukkit.plugin.CommandManager;
 import org.bukkit.plugin.Plugin;
 import org.bukkit.plugin.PluginManager;
+import org.bukkit.plugin.SimpleCommandManager;
 import org.bukkit.plugin.SimplePluginManager;
 import org.bukkit.plugin.java.JavaPluginLoader;
 
@@ -19,6 +21,7 @@ public final class CraftServer implements Server {
     private final String serverName = "Craftbukkit";
     private final String serverVersion = "1.2_01";
     private final PluginManager pluginManager = new SimplePluginManager(this);
+    private final CommandManager commandManager = new SimpleCommandManager();
 
     protected final MinecraftServer console;
     protected final ServerConfigurationManager server;
@@ -38,7 +41,11 @@ public final class CraftServer implements Server {
                 Plugin[] plugins = pluginManager.loadPlugins(pluginFolder);
 
                 for (Plugin plugin : plugins) {
-                    pluginManager.enablePlugin(plugin);
+                    if (commandManager.registerCommands(plugin)) {
+                        pluginManager.enablePlugin(plugin);       
+                    } else {
+                        Logger.getLogger(CraftServer.class.getName()).log(Level.SEVERE, "Plugin " + plugin.getDescription().getName() + " failed to load. Reason: Requested commands already in use.");
+                    }
                 }
             } catch (Throwable ex) {
                 Logger.getLogger(CraftServer.class.getName()).log(Level.SEVERE, ex.getMessage() + " (Is it up to date?)", ex);
@@ -133,4 +140,8 @@ public final class CraftServer implements Server {
     public ServerConfigurationManager getHandle() {
         return server;
     }
+
+    public boolean dispatchCommand(Player player, String cmd) {
+        return commandManager.dispatchCommand(player, cmd);
+    }
 }