public static ExtendedCell createMobRefCell(ExtendedCell cell, byte[] fileName,
    Tag tableNameTag) {
    // Append the tags to the KeyValue.
    // The key is same, the value is the filename of the mob file
    List<Tag> tags = new ArrayList<>();
    // Add the ref tag as the 1st one.
    tags.add(MobConstants.MOB_REF_TAG);
    // Add the tag of the source table name, this table is where this mob file is flushed
    // from.
    // It's very useful in cloning the snapshot. When reading from the cloning table, we need to
    // find the original mob files by this table name. For details please see cloning
    // snapshot for mob files.
    tags.add(tableNameTag);
    return createMobRefCell(cell, fileName, TagUtil.fromList(tags));
  }
Creates a mob reference KeyValue. The value of the mob reference KeyValue is mobCellValueSize +
mobFileName.
@param cell         The original Cell.
@param fileName     The mob file name where the mob reference KeyValue is written.
@param tableNameTag The tag of the current table name. It's very important in cloning the
                    snapshot.
@return The mob reference KeyValue.
hbase-server/src/main/java/org/apache/hadoop/hbase/mob/MobUtils.java