$ git clone -n https://src.fedoraproject.org/rpms/maxima.git /var/lib/mock/f42-build-3272231-41305/root/chroot_tmpdir/scmroot/maxima
Cloning into '/var/lib/mock/f42-build-3272231-41305/root/chroot_tmpdir/scmroot/maxima'...
$ git fetch origin 4602e3dd5c5dccd03e11976cba40e6bbda82e6a3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/maxima
 * [new ref]         4602e3dd5c5dccd03e11976cba40e6bbda82e6a3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4602e3d Fix for https://fedoraproject.org/wiki/Changes/TclTk9.0 (rhbz#2337728)