$ git clone -n https://src.fedoraproject.org/rpms/R-qpdf.git /var/lib/mock/f42-build-side-1-3499326-45964/root/chroot_tmpdir/scmroot/R-qpdf
Cloning into '/var/lib/mock/f42-build-side-1-3499326-45964/root/chroot_tmpdir/scmroot/R-qpdf'...
$ git fetch origin edb6cffc3f8fa3b983d873cdd77fd538faeb939c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-qpdf
 * [new ref]         edb6cffc3f8fa3b983d873cdd77fd538faeb939c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at edb6cff R-maint-sig mass rebuild