Patch DimensionSavedDataManager to not spam FS mkdirs requests for

empty files that don't exist yet, and don't contain data. Should
result in a significant performance improvement for those with slower disks.

Signed-off-by: cpw <cpw+github@weeksfamily.ca>

patches/minecraft/net/minecraft/world/storage/DimensionSavedDataManager.java.patch

@@ -0,0 +1,20 @@
+--- a/net/minecraft/world/storage/DimensionSavedDataManager.java
++++ b/net/minecraft/world/storage/DimensionSavedDataManager.java
+@@ -38,6 +38,7 @@
+    @Nullable
+    public <T extends WorldSavedData> T func_201067_a(Function<String, T> p_201067_1_, String p_201067_2_) {
+       WorldSavedData worldsaveddata = this.field_212778_c.get(p_201067_2_);
++      if (worldsaveddata == net.minecraftforge.common.util.DummyWorldSaveData.DUMMY) return null;
+       if (worldsaveddata == null && this.field_212780_e != null) {
+          try {
+             File file1 = this.field_212780_e.func_212423_a(this.field_212777_b, p_201067_2_);
+@@ -45,6 +46,9 @@
+                worldsaveddata = (WorldSavedData)p_201067_1_.apply(p_201067_2_);
+                worldsaveddata.func_76184_a(func_212774_a(this.field_212780_e, this.field_212777_b, p_201067_2_, 1631).func_74775_l("data"));
+                this.field_212778_c.put(p_201067_2_, worldsaveddata);
++            } else {
++               this.field_212778_c.put(p_201067_2_, net.minecraftforge.common.util.DummyWorldSaveData.DUMMY);
++               return null;
+             }
+          } catch (Exception exception) {
+             field_212776_a.error("Error loading saved data: {}", p_201067_2_, exception);

src/main/java/net/minecraftforge/common/util/DummyWorldSaveData.java

@@ -0,0 +1,22 @@
+package net.minecraftforge.common.util;
+
+import net.minecraft.nbt.NBTTagCompound;
+import net.minecraft.world.storage.WorldSavedData;
+
+public class DummyWorldSaveData extends WorldSavedData {
+    public static final DummyWorldSaveData DUMMY = new DummyWorldSaveData();
+    private DummyWorldSaveData() {
+        super("DUMMYDUMMY \uD83D\uDC4C\uD83D\uDC4C\uD83D\uDC4C");
+    }
+
+    @Override
+    public void read(final NBTTagCompound nbt) {
+        // NOOP
+    }
+
+    @Override
+    public NBTTagCompound write(final NBTTagCompound compound) {
+        // NOOP
+        return null;
+    }
+}