Git(hub) plugin and triggering freestyle build based on comment string in PR

[Ramanathan Muthaiah]

In our enterprise setup, we have bunch of 'freestyle' jobs that use Github pullrequest builder plugin (GHPRB)  -- in the config of these jobs, it it setup to look for certain words in the incoming pull requests (PRs). This setup is working without any problems.

We want to consolidate the use of such external plugins. Specifically, to move away from GHPRB plugin and start using the suite of plugins related to Git, and Github.

However, it seems migrating the freestyle jobs to re-use (already installed and used for pipeline build jobs) the suite of Git and GitHub plugins, it is not possible(?) to trigger fresh builds for the incoming PR by scanning the comments. Is this true (that this functionality cannot be achieved with this combination of freestyle + git* plugins)? 

Would be interested to know if anyone has explored this and got it working?

/Ram

P.S: 

Eclipse' CI infra hosts several builds jobs for JGit. One among them is pipeline style build setup -- https://ci.eclipse.org/jgit/job/stable/job/jgit.gerrit-pipeline/. In the landing page, it is claimed that ". . . can also be triggered by a comment containing "trigger build" "