HADOOP-11661. Deprecate FileUtil#copyMerge. Contributed by Brahma Reddy Battula.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileUtil.java

@@ -381,6 +381,7 @@ public class FileUtil {
 
   }
 
+  @Deprecated
   /** Copy all files in a directory to one output file (merge). */
   public static boolean copyMerge(FileSystem srcFS, Path srcDir,
                                   FileSystem dstFS, Path dstFile,

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestFileUtil.java

@@ -559,6 +559,7 @@ public class TestFileUtil {
    * @return boolean true if the call to FileUtil.copyMerge was successful.
    * @throws IOException if an I/O error occurs.
    */
+  @SuppressWarnings("deprecation")
   private boolean copyMerge(String src, String dst)
       throws IOException {
     Configuration conf = new Configuration();