$ git clone -n https://src.fedoraproject.org/rpms/re2c.git /var/lib/mock/f45-build-34381-685/root/chroot_tmpdir/scmroot/re2c
Cloning into '/var/lib/mock/f45-build-34381-685/root/chroot_tmpdir/scmroot/re2c'...
$ git fetch origin 7b5840e35fecc278080ed94c9b40c60961a29979:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/re2c
 * [new ref]         7b5840e35fecc278080ed94c9b40c60961a29979 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7b5840e Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild