Feat: having a whitelist flag

[pascalandy]

Hi,
I see the value of having a --env BLACKLIST_SERVICES.

In my case I would like to be more granular way to select only a few services that will be impacted by shepherd. I run about 60 services at the moment and only 3 of them (QA stuff) should be impacted by shepherd.

Example

--env ONLY_SERVICES="webapp1 webapp2 webappdev"

Thanks for your work!

[djmaze]

That feature would be a welcome addition from my standpoint. As I currently do not need this myself, I am open for PRs!

[pascalandy]

I won't do it and it's not a big deal. Closing but still, I would love it :)