I want to add env variables to new instances

I want all my deployments to have access to postgres, thus I'm creating a plugin which sets up a new user with access to a new database (on a postgres server in a different container). I want to expose the database access with an env variable, just like heroku does. To me it looks like release is the best place to put this hook.
Added X-Forwarded-For to pass client IP to backend
Build image from Dockerfile instead of curl S3
Add git & dokku to the docker group, creating it if it doesn't exist.
Merge pull request #173 from rhy-jot/2013-08-13/docker-group

Add git & dokku to the docker group, creating it if it doesn't exist.
Mention and link plugin page in the readme
Merge pull request #145 from msumpter/patch-2

Added X-Forwarded-For to pass client IP to backend
Redeploy apps on reboot, fixes #82
Merge pull request #178 from asm89/redeploy

Redeploy apps on reboot, fixes #82
Merge pull request #134 from phaza/patch-1

I want to add env variables to new instances
Merge pull request #168 from Kloadut/docker-build

Build image from Dockerfile instead of curling S3
remove leading 'remote:' from git output
Merge pull request #179 from kubenstein/master

Remove leading 'remote:' from git output
Remove redundant command from dokku-standard plugin
Fix that only the output the last plugin command is shown

Plugin "commands" should end with "cat" because the output of each
plugin's command is piped through the next one by pluginhook
Merge branch 'master' of https://github.com/Kloadut/dokku
Move delete action to 00_dokku-standard plugin
Remove .swp file