First I just want to say this is a really amazing plugin and aside from this one problem our group is really happy with it.

We currently have a matrix project to test on multiple systems. Unfortunately we have a problem when new commits are pushed to a pull request. The main build of the matrix project will always get the correct revision, but the matrix builds end up building the the previous revision. The matrix builds are consistently one revision behind. I suspect it has something to do with the interaction between this line of code in GhprbTrigger.java

// add the previous pr BuildData as an action so that the correct change log is generated by the GitSCM plugin
// note that this will be removed from the Actions list after the job is completed so that the old (and incorrect)
// one isn't there
return this.job.scheduleBuild2(job.getQuietPeriod(), cause, new ParametersAction(values), findPreviousBuildForPullId(pullIdPv));

and the method determineRevisionToBuild in GitSCM.java in the git-plugin. I am willing to help resolve the issue, but I don't know enough to setup a unit test that reproduces the problem so it can be resolved.

You can see an example where this is happening here: https://acdl.mit.edu/csi/job/gpkit_PullRequest/377/

Thank you,
Marshall