Mention that bundle docker images can be in private registries

[christophermaier]

From @vanstee on October 14, 2016 15:20

pygillier [11:14 AM]  
hi all, can we pull docker images for commands from privates registries ?

vanstee [11:15 AM]  
@pygillier You should be able to. Relay has env var/config vars that you can set to auth with dockerhub or another registry. https://github.com/operable/go-relay/blob/master/example_relay.conf#L112-L133
 GitHub
operable/go-relay
go-relay - Cog Relay written in Go supporting Docker and simple command bundles  

[11:17]  
Let me know if you have any trouble with it though. I know there was some weirdness with quay.io in the past

pygillier [11:17 AM]  
okay, I'll test it on my registry

[11:18]  
(the doc on writing bundles should be updated as it doesn't state we can use private registries) http://docs.operable.io/docs/bundle-configs
Cog
Bundle Configs · Cog
Documentation for Cog, the next-generation ChatOps platform from Operable. (3KB)

Copied from original issue: operable/cog#1054