I want to point out the CHANGE_* variables ARE populated when then build is started from a pull request on a forked repository. When I attempt to create a branch on the main repository then create a pull request to merge into master, the variables are not populated (not entirely sure how it determines what a pull request "is" in that case).

Could you please also add following variables:
Source_branch
Repository_owner (organization)
repository_name
sha (commit_sha)
the last one is very important

maniax89 I was struggling with this as well and found that changing the configuration from Build origin branches also filed as PRs (default checked) to Build origin PRs (merged with base branch) was enough to get the env vars set in my jobs.

Seems like this was a configuration error (that the configuration options are non-obvious is a separate issue)... Closing this issue in any case as with the 2.0 series of GitHub Branch Source the GitHub Organization Folders plugin is dead (functionality moved to GitHub Branch Source)

I got same problems when sending 

${CHANGE_TITLE} ${CHANGE_AUTHOR} ${CHANGE_TARGET} ${CHANGE_AUTHOR_DISPLAY_NAME}

with Chatwork Plugin

I also tried this way too

$CHANGE_TITLE $CHANGE_AUTHOR $CHANGE_TARGET $CHANGE_AUTHOR_DISPLAY_NAME

> Seems like this was a configuration error (that the configuration options are non-obvious is a separate issue)

No. It's more than that. I think something is wacky here.  It may just be the case that GitHub items should have different variables (e.g. PR_ vars) or something.

My users (about 200 developers) are constantly tripping on this.  Some of the variables seem to imply they should always be set, instead of just for a PR.  e.g. If I push a new commit, shouldn't there be a record of the changes that triggered it?  Regardless of whether you are doing a "merged with base" or not.