A Heroku buildpack for setting the ssh private key as part of the application build.
In the Heroku Dashboard for your app, add this buildpack (the repo URL), and make sure it is first.
Set the private key environment variable
SSH_KEY of your Heroku app (must be base64 encoded).
$ heroku config:set SSH_KEY=$(cat path/to/your/keys/id_rsa | base64)
By default the buildback adds Github to
known_hosts. However you can configure your app to allow custom hosts, too.
All that's needed is the set
SSH_HOSTS for you app to a comma-delimited list of hosts, e.g.
$ heroku config:set SSH_HOSTS="firstname.lastname@example.org,example.com"
Copy the snippet above into CLI.