Add RebuildDispatcher extension point to allow other plugins to propa…

[bjacklyn]

…gate additional actions to the rebuild

[bjacklyn]

Inspiration from comments in this PR.

This change allows me to create a RebuildDispatcher and add the RevisionParameterAction (from the git-plugin). The dispatcher needs to be able to add new Actions because the original build does not necessarily have a RevisionParameterAction itself, so only copying actions is insufficient.

Git plugin impl:

@Extension
public class GitPluginRebuildDispatcher extends RebuildActionDispatcher {

    @Override
    public Collection<Action> getPropagatingActions(Run run) {
        List<Action> actions = Lists.newArrayList();

        BuildData buildData = run.getAction(BuildData.class);
        if (buildData != null) {

            Build build = buildData.lastBuild;
            if (build != null) {
                Revision revision = build.marked;
                if (revision == null) {
                    revision = build.revision;
                }

                if (revision != null) {
                    // Don't let the git plugin revert the BuildData of these branch(es) to this revision.
                    // Otherwise the git plugin will also rebuild the HEAD of all of these branches on the next SCM poll (yuck).
                    Revision revisionWithoutBranches = new Revision(revision.getSha1(), Collections.<Branch>emptyList());

                    actions.add(new RevisionParameterAction(revisionWithoutBranches));
                }
            }
        }

        return actions;
    }
}

[ctran]

These pom changes don't seem to be necessary for this PR.