$ git clone -n https://src.fedoraproject.org/rpms/R-pdftools.git /var/lib/mock/f41-build-845859-162818/root/chroot_tmpdir/scmroot/R-pdftools
Cloning into '/var/lib/mock/f41-build-845859-162818/root/chroot_tmpdir/scmroot/R-pdftools'...
$ git fetch origin 3cd8dbcf74fdf83b013a574d1eb8ae2eae181ec3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-pdftools
 * [new ref]         3cd8dbcf74fdf83b013a574d1eb8ae2eae181ec3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3cd8dbc Disable bootstrap