def build_from_file(file)
      dir = File.dirname(file)
      string = IO.read(file)
      build_from_string(string, dir)
    end
def build_from_file(file)
      dir = File.dirname(file)
      string = IO.read(file)
      build_from_string(string, dir)
    end
Builds the image from a file that is not called *Dockerfile*.

 It also saves the generated image in the object internally.

 This creates a temporary directory where it copies all the files and
 generates the temporary Dockerfile.

 @param file [String] The Dockerfile file path.

 @return void

 @api private