How to Access files on Heroku?

I don't think this is possible, for one reason: A Heroku dyno has it's own ephemeral filesystem with a git checkout of the most recent code. It cannot go the other way around however, it's not possible to check file changes in the dyno in into the git repo. This is why you get the response 'Already up-to-date.' when trying to pull, because the heroku git remote is inn sync with your local repo.

You should maybe store your file on Amazon's S3 or in a database or even write your data to a database, so that it is persisted between heroku deployments.

You can run heroku run bash and backup the file then deploy your app run heroku run bash again and remove the new file and replace it with the old one you backed up. Hope it helps