$ git clone -n https://src.fedoraproject.org/rpms/rebase-helper.git /var/lib/mock/f42-build-side-1-3583689-46890/root/chroot_tmpdir/scmroot/rebase-helper
Cloning into '/var/lib/mock/f42-build-side-1-3583689-46890/root/chroot_tmpdir/scmroot/rebase-helper'...
$ git fetch origin 4330ac2e672d7f98ac60085abbca9260f61e5c49:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rebase-helper
 * [new ref]         4330ac2e672d7f98ac60085abbca9260f61e5c49 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4330ac2 Update to 0.29.5 upstream release