title: passing envvars to docker containers in GoCD
body: <p>We have a docker container and the program that runs inside expects a number of envvars to be set. There are several ways to do this and I was curious as to what the correct way is:</p>
  
  <p>1- put envvars in a config repo, add it as a material, use docker --env-file flag to pass the file. Cons: seems like overkill for passing 10 envvars.</p>
  
  <p>2- define envvars in the job configuration tab. Export them during docker build. Cons: Every new job would have to manually set the envvars, adding an envvar would require changing all jobs in one place.</p>
  
  <p>3- define envvars in the job configuration tab. Pass them during docker run using -e flag. Cons: Every new job would have to manually set the envvars, adding an envvar would require changing each job in two places.</p>
  
  <p>Is there any other way?</p>