From a discussion on the docker-user mailing list:

It would be nice if the Dockerfile could be included in the image itself.

• it could be used by docker hub to display the source of the image
• if you pull an image from some other registry it would give you some idea of how the image was built

@erikh raised the concern that this could be bad for images with secrets.

This could be implemented as a new flag to docker build which would optionally allow you to include the file. That way any image with secrets could omit the flag, for the old behaviour.

docker build --include-dockerfile or something like that?