The command is:
/home/phabricator-android-builder/repos/libre-busto-ci-cd/bin/publish-latest-branch-build.sh ${buildable.revision}
Source code:
https://gitpull.it/source/libre-busto-ci-cd/browse/master/bin/publish-latest-branch-build.sh
(ex P23)
This step will copy the built .apk to an indexed HTTP directory exposed by Apache, signing them: