craftbukkit/nms-patches/net/minecraft/world/level/block/BlockCommand.patch

--- a/net/minecraft/world/level/block/BlockCommand.java
+++ b/net/minecraft/world/level/block/BlockCommand.java
@@ -26,6 +26,8 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
+import org.bukkit.event.block.BlockRedstoneEvent; // CraftBukkit
+
 public class BlockCommand extends BlockTileEntity implements GameMasterBlock {
 
     private static final Logger LOGGER = LogManager.getLogger();
@@ -56,6 +58,15 @@
                 TileEntityCommand tileentitycommand = (TileEntityCommand) tileentity;
                 boolean flag1 = world.isBlockIndirectlyPowered(blockposition);
                 boolean flag2 = tileentitycommand.f();
+                // CraftBukkit start
+                org.bukkit.block.Block bukkitBlock = world.getWorld().getBlockAt(blockposition.getX(), blockposition.getY(), blockposition.getZ());
+                int old = flag2 ? 15 : 0;
+                int current = flag1 ? 15 : 0;
+
+                BlockRedstoneEvent eventRedstone = new BlockRedstoneEvent(bukkitBlock, old, current);
+                world.getCraftServer().getPluginManager().callEvent(eventRedstone);
+                flag1 = eventRedstone.getNewCurrent() > 0;
+                // CraftBukkit end
 
                 tileentitycommand.a(flag1);
                 if (!flag2 && !tileentitycommand.g() && tileentitycommand.t() != TileEntityCommand.Type.SEQUENCE) {