func RegisterPullRequestHandler(name string, fn PullRequestHandler, help HelpProvider) {
	pluginHelp[name] = help
	pullRequestHandlers[name] = fn
}
func RegisterPullRequestHandler(name string, fn PullRequestHandler, help HelpProvider) {
	pluginHelp[name] = help
	pullRequestHandlers[name] = fn
}
// RegisterPullRequestHandler registers a plugin's github.PullRequestEvent handler.