code: public FileAssert hasContentEqualTo(File expected, Charset charset) {
      files.assertEqualContent(description, actual, expected, charset);
      return this;
    }
docs: Verifies that the content of the file represented by the <em>actual</em> {@code File} is equal to the content of
  the file represented by the given {@code File}. It is assumed that the content of the files is text.
  
  @param expected the <em>expected</em> {@code File}.
  @param charset the charset to use when reading the contents of the {@code File}s.
  @return {@code this} assertion object.
  @throws NullPointerException if the <em>expected</em> {@code File} is {@code null}.
  @throws IllegalArgumentException if the <em>expected</em> {@code File} does not represent an existing file.
  @throws NullPointerException if the given charset is {@code null}.
  @throws AssertionError if the <em>actual</em> {@code File} is {@code null}.
  @throws AssertionError if the <em>actual</em> {@code File} does not represent an existing file.
  @throws IORuntimeException if an I/O error occurs.
  @throws AssertionError if the content of the file represented by the <em>actual</em> {@code File} is not equal to
  the content of the file represented by the given {@code File}.