Added detection of McRegion-format worlds for snapshot detection.

src/com/sk89q/worldedit/data/ChunkStore.java

@@ -75,4 +75,11 @@ public abstract class ChunkStore {
     public void close() throws IOException {
 
     }
+    
+    /**
+     * Returns whether the chunk store is of this type.
+     * 
+     * @return
+     */
+    public abstract boolean isValid();
 }

src/com/sk89q/worldedit/data/FileLegacyChunkStore.java

@@ -62,4 +62,9 @@ public class FileLegacyChunkStore extends LegacyChunkStore {
             throw new MissingChunkException();
         }
     }
+
+    @Override
+    public boolean isValid() {
+        return true; // Yeah, oh well
+    }
 }

src/com/sk89q/worldedit/data/FileMcRegionChunkStore.java

@@ -54,4 +54,9 @@ public class FileMcRegionChunkStore extends McRegionChunkStore {
         }
     }
 
+    @Override
+    public boolean isValid() {
+        return new File(path, "region").isDirectory();
+    }
+
 }

src/com/sk89q/worldedit/data/TrueZipLegacyChunkStore.java

@@ -164,4 +164,9 @@ public class TrueZipLegacyChunkStore extends LegacyChunkStore {
     public void close() throws IOException {
         zip.close();
     }
+
+    @Override
+    public boolean isValid() {
+        return true; // Yeah, oh well
+    }
 }

src/com/sk89q/worldedit/data/ZippedAlphaChunkStore.java

@@ -161,4 +161,9 @@ public class ZippedAlphaChunkStore extends LegacyChunkStore {
     public void close() throws IOException {
         zip.close();
     }
+
+    @Override
+    public boolean isValid() {
+        return true; // Yeah, oh well
+    }
 }

src/com/sk89q/worldedit/snapshots/Snapshot.java

@@ -73,8 +73,14 @@ public class Snapshot {
                 throw new DataException("TrueZIP is required for .tar support");
             }
         } else {
+            ChunkStore chunkStore = new FileMcRegionChunkStore(file);
+            
+            if (!chunkStore.isValid()) {
                 return new FileLegacyChunkStore(file);
             }
+            
+            return chunkStore;
+        }
     }
 
     /**