$ git clone -n https://src.fedoraproject.org/rpms/grive2.git /var/lib/mock/f45-build-13030-446/root/chroot_tmpdir/scmroot/grive2
Cloning into '/var/lib/mock/f45-build-13030-446/root/chroot_tmpdir/scmroot/grive2'...
$ git fetch origin 87838b1baf8fd83b5884f795ce802a65c3ad862a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/grive2
 * [new ref]         87838b1baf8fd83b5884f795ce802a65c3ad862a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 87838b1 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild