title: safe way to use build-time argument in Docker
body: <p>I have a build time Argument with which I would like to build my Docker file; Since that argument is confidential in nature (github key of a private repo) I don't want that to end up in a docker image. This quotes is from official docker documentation regarding the build-time arguments.</p>
  
  <blockquote>
    <p>Warning: It is not recommended to use build-time variables for passing
    secrets like github keys, user credentials etc. Build-time variable
    values are visible to any user of the image with the docker history
    command.</p>
  </blockquote>
  
  <p>Anybody know what is the recommended way to achieve the same?</p>