download file from heroku dyno

#$ heroku help ps:copy 
Copy a file from a dyno to the local filesystem

USAGE
  $ heroku ps:copy FILE

OPTIONS
  -a, --app=app        (required) app to run command against
  -d, --dyno=dyno      specify the dyno to connect to
  -o, --output=output  the name of the output file
  -r, --remote=remote  git remote of app to use

DESCRIPTION
 
 Example:

$ heroku ps:copy FILENAME --app murmuring-headland-14719