Fix of bug in FileUtil - do not empty the file if one tries to copy it into itself.

platform/util/src/com/intellij/openapi/util/io/FileUtil.java

@@ -459,6 +459,7 @@ public class FileUtil extends FileUtilRt {
 
   @SuppressWarnings("Duplicates")
   private static void performCopy(@NotNull File fromFile, @NotNull File toFile, final boolean syncTimestamp) throws IOException {
+    if (filesEqual(fromFile, toFile)) return;
     final FileOutputStream fos;
     try {
       fos = openOutputStream(toFile);