def if_file_changed(file, &block)
      if_string_changed(file, Digest::SHA256.file(file).hexdigest.to_s, &block)
    end
def if_file_changed(file, &block)
      if_string_changed(file, Digest::SHA256.file(file).hexdigest.to_s, &block)
    end
If the digest of the file is different from the stored digest, execute the block.