$ git clone -n https://src.fedoraproject.org/rpms/gnome-shell.git /var/lib/mock/f39-build-1646629-40412/root/chroot_tmpdir/scmroot/gnome-shell
Cloning into '/var/lib/mock/f39-build-1646629-40412/root/chroot_tmpdir/scmroot/gnome-shell'...
$ git fetch origin 32c32e05111568f59ec3dd7bbfd6a50e2ea5598c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gnome-shell
 * [new ref]         32c32e05111568f59ec3dd7bbfd6a50e2ea5598c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 32c32e0 Update to 45.1