Support per-PR build environments

[smashwilson]

Is it possible to have PR builds that always build to the same staging branch, instead of creating a new version for each PR update?

Use case: For content in development, having a single staging URL for the content that is not tied to PRs would make it easier to provide all reviewers with the same staging URL throughout project development.

Yes, possible and totally reasonable.

Separated out from rackerlabs/nexus-control#369.

[smashwilson]

I'm suggesting to have a configurable option if people want to provide a stable URL for content in beta or development.

Not a configuration option - Strider is configured completely automatically and is meant to be as hands-off as possible.

What I'm thinking instead is detecting a @rackernexus command phrase in the pull request description or comments. That'll let you opt in to build environment re-use for specific pull requests and make it clearer what's going on for anyone watching.

[meker12]

I like the idea of having a command phrase. That's kind of what I had in mind--so you can enable and disable as needed. I'll be following along. This would help the RPC team with their new doc release, I think.