$ git clone -n https://src.fedoraproject.org/rpms/mathjax.git /var/lib/mock/f45-build-18108-508/root/chroot_tmpdir/scmroot/mathjax
Cloning into '/var/lib/mock/f45-build-18108-508/root/chroot_tmpdir/scmroot/mathjax'...
$ git fetch origin 31ffad03b272427fff8f4300515ca578152d9484:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mathjax
 * [new ref]         31ffad03b272427fff8f4300515ca578152d9484 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 31ffad0 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild