Use the heroku buildpack profile.d scripts mechanism to set the MONGO_URL environment variable to MONGOHQ_URL if present. If you provided the MONGO_URL by yourself in your app settings, it won't be overriden.
The buildpack now check whether you added the Mailgun addon and if you did, set the MAIL_URL environment variable to:
"smtp://${MAILGUN_SMTP_LOGIN}:${MAILGUN_SMTP_PASSWORD}@${MAILGUN_SMTP_SERVER}:${MAILGUN_SMTP_PORT}"
If you provided the MAIL_URL by yourself in your app settings, it won't be overriden.
- remove build asset caching
- prevent installation of devDependencies
- add warning if no nodejs version specified