$ git clone -n https://src.fedoraproject.org/rpms/R-knitr.git /var/lib/mock/f45-build-6218-347/root/chroot_tmpdir/scmroot/R-knitr
Cloning into '/var/lib/mock/f45-build-6218-347/root/chroot_tmpdir/scmroot/R-knitr'...
$ git fetch origin 25578be1bbe005900ac94b5d7a8bf5aa9ae06c66:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-knitr
 * [new ref]         25578be1bbe005900ac94b5d7a8bf5aa9ae06c66 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 25578be Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild