code: public OutputStream appendFile(@NotNull final Transaction txn, @NotNull final File file) {
          return new VfsAppendingStream(this, txn, file, new LastModifiedTrigger(txn, file, pathnames));
      }
docs: Returns {@linkplain OutputStream} to write the contents of the specified file from the end of the file. If the
  file is empty the contents is written from the beginning.
  
  @param txn  {@linkplain Transaction} instance
  @param file {@linkplain File} instance
  @return @linkplain OutputStream} to write the contents of the specified file from the end of the file
  @see #readFile(Transaction, File)
  @see #readFile(Transaction, long)
  @see #readFile(Transaction, File, long)
  @see #writeFile(Transaction, File)
  @see #writeFile(Transaction, long)
  @see #writeFile(Transaction, File, long)
  @see #writeFile(Transaction, long, long)
  @see #touchFile(Transaction, File)