[do not merge] Enable rebuild triggers

[twaugh]

This pull request is for enabling rebuild triggers, and should only be merged once all the plug-ins necessary for them to work are configured.

• check_and_set_rebuild plug-in (Enable rebuild-related plugins only if there are triggers #213)
• bump_release plug-in (Configure bump_release plugin #214)
• import_image plug-in (Imagestream naming #194)
• sendmail plugin for failed build notifications (Create exit_sendmail plugin atomic-reactor#282, Configure sendmail plugin #248)
• koji_promote plug-in (Plugin for promoting builds to Content Generator API atomic-reactor#319, Configure koji_promote plugin #282)

[twaugh]

Question: do we want 'simple'-type builds to have automated rebuilds, or only 'prod'-type builds?

[bkabrda]

Originally, I thought we could have autorebuilds for all types of builds, but now I'm starting to see that it may be problematic, cause autorebuilds need a whole bunch of plugins to work etc... I guess noone is actually using simple builds in production, so we may as well drop the autorebuild support for them (and, if someone does want to use them in production, he may as well change the input jsons).

So I'm +1 for dropping autorebuild support in simple builds.

[mmilata]

Agree with @bkabrda, I don't see a use case for simple builds with autorebuilds.

[twaugh]

I've updated this so that the bump_release and import_image plugins are removed from prod bulids unless there are triggers present. I think with this change we might be able to merge this (minus the actual trigger JSON) sooner, without needing to wait for all the pieces.

[bkabrda]

Note: this carries some significant changes that should be documented in docs/build_process.md. (notably, I think we should explain why we change git ref in BuildConfig to git branch).

[twaugh]

Agreed.

I've started separating this into bits that can be merged now and bits that need to wait. #213 is all for bits that are ready now, and once the bump_release plugin in merged in atomic-reactor I'll submit a new PR for enabling/configuring that -- and documenting the branch/commit swap.

Then this PR will be left with just adding the trigger.

[landscape-bot]

Code quality remained the same when pulling fb14e07 on projectatomic:enable-rebuild-triggers into ead70c2 on projectatomic:master.

[lcarva]

@twaugh, given that #640 uses the configuration file in repository to enable autorebuilds, and it's disabled by default, can we safely merge this (after conflicts are resolved)?

[twaugh]

Yes, seems like that would be safe.

[twaugh]

Closing in favour of #720.