$ git clone -n https://src.fedoraproject.org/rpms/gnome-font-viewer.git /var/lib/mock/f40-build-802215-143961/root/chroot_tmpdir/scmroot/gnome-font-viewer
Cloning into '/var/lib/mock/f40-build-802215-143961/root/chroot_tmpdir/scmroot/gnome-font-viewer'...
$ git fetch origin b9738344d2229e2f471e9f1e65f0106b3b8df1db:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gnome-font-viewer
 * [new ref]         b9738344d2229e2f471e9f1e65f0106b3b8df1db -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b973834 Update to 46.0