Starting a new thread to consolidate some thoughts in the other two threads...

After reading through the github migration threads and wiki, I see it actually involves a few different things:
- The actual migration.
- Proposed pull-request workflows.
- The split to multiple repositories.
- Versioning schemes.

The actual migration plan is detailed and Heiko looks to have done a good job of mapping out the details of how it will happen, including a dry-run.

The new workflows look promising, especially from a code-review perspective. I think we'll need that written up more formally for ourselves and contributors. And maybe have a good demo for the team so people (like me) get a good grasp of what we'll be doing.  These processes are also something we can modify as we go.

I'm OK with the idea of breaking RHQ into 3 pieces, core, plugins, and helpers.  I think it will be helpful to plugin developers to potentially work with a smaller codebase, and a clearly identified helper project.   I also think the decision to avoid further granularity is a good one.  We will need to add some Jenkins jobs, but I don't think it will be an unmanageable number (it's not 3 times the number we have today).  And we will likely need to update our release processes, again.  Keeping the platform plugin in core makes sense so that core can actually run on its own, and also for anyone that plans to use only custom plugins.

It's the proposed dependency versioning that I'm questioning.

I'm not convinced there is real benefit to plugin writers or contributors by having rhq-plugins/master depend on a released version of rhq-core. In short, what's wrong with instead asking the developer to git checkout rhq-plugins/release-X rather than rhq-plugins/master?

A plugin developer does not need to build rhq-plugins/master to develop a new plugin. On the other hand, rhq-helpers/master, plugin-gen in particular, would benefit from depending on released artifacts.  In that case the plugin dev could build the generator easily, against deps published in central, and run a real server/agent of the same version, installed from product dists.

As for working on an existing plugin; an enhancement or bug fix could be built against rhq-plugins/release-X. Rhq-plugins/release-X is easily built against central. The feature or fix would be compatible with the published version of core.

Using 4.6 as an example, if we had an rhq-plugins/release-4.6 branch, a developer could opt to build this branch against the published artifacts, and make a fix or enhancement to the 4.6 plugin.  Work committed here could be cherry-picked to master as needed. If in fact the developer or contributor elected to work with master they certainly could, in the same manner as today, by building rhq-core/master and working with the snapshot version.

As a further example, let's say someone finds a bug in the 4.6 AS7 plugin.  It could be fixed against rhq-plugins/release-4.6 by anyone, without having to build core.  It could also be fixed in rhq-plugins/master with a full dev environment, and cherry-picked back.  And rhq-plugins-4.6.1 could be released without a need to release a new core/server.

The current proposal on the wiki is to have rhq-plugins/master depend on rhq-core's current release version, and not on rhq-core/master's snapshot version. This will certainly make development more difficult.  One immediate example will be the new provisioning implementation.  This feature development will involve new facets, change to the plugin descriptor, and introduce other dependencies between plugin code and the [core] container.  A strategy that forces the plugin code to conform to rhq-core's release version will make this very hard.

Let's talk a bit about plugin/core compatibility.  As it stands today (I believe) an agent plugin can be dropped into an RHQ server, and we don't really validate it, we assume that it is compatible. Assuming the plugin descriptor parses, and metadata updates succeed, we're good on the server and the agent is free to pull it down.  It's pretty loose.  That doesn't really have to change.  Plugin release cadence is not really dependent on rhq-server version.  It simply has to be compatible.  Developing against a release version will give you that and (unless using deprecated features that are going away) will give you compatibility with the next release.  But, to ensure timely release of a plugin leveraging new features of core, it must be easily developed against core's snapshot version.  To prevent this will make things difficult, likely force unnecessary core releases, and create lag times between core and plugin releases.

The benefit of being able to check out and build rhq-plugins/master without needing to also build rhq-core/master, does not seem to be enough to merit the downside to plugin development and release.