$ git clone -n https://src.fedoraproject.org/rpms/R-pdftools.git /var/lib/mock/f38-build-side-42-init-devel-1390697-30718/root/chroot_tmpdir/scmroot/R-pdftools
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-1390697-30718/root/chroot_tmpdir/scmroot/R-pdftools'...
$ git fetch origin 38f18a5443ce7bde874555e3e0c11fb6e1fce563:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-pdftools
 * [new ref]         38f18a5443ce7bde874555e3e0c11fb6e1fce563 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 38f18a5 R-maint-sig mass rebuild