public static ParsedDelta parsedDelta(Path deltaDir, FileSystem fs) throws IOException {
    return parsedDelta(deltaDir, fs, null);
  }
This will look at a footer of one of the files in the delta to see if the
file is in Acid format, i.e. has acid metadata columns.  The assumption is
that for any dir, either all files are acid or all are not.
ql/src/java/org/apache/hadoop/hive/ql/io/AcidUtils.java