$ git clone -n https://src.fedoraproject.org/rpms/pkgdiff.git /var/lib/mock/f45-build-28577-631/root/chroot_tmpdir/scmroot/pkgdiff
Cloning into '/var/lib/mock/f45-build-28577-631/root/chroot_tmpdir/scmroot/pkgdiff'...
$ git fetch origin 57cccf41d85146897e16a08ada22bc818f0843d4:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/pkgdiff
 * [new ref]         57cccf41d85146897e16a08ada22bc818f0843d4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 57cccf4 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild