$ git clone -n https://src.fedoraproject.org/rpms/glibmm2.4.git /var/lib/mock/f38-build-722424-98805/root/chroot_tmpdir/scmroot/glibmm2.4
Cloning into '/var/lib/mock/f38-build-722424-98805/root/chroot_tmpdir/scmroot/glibmm2.4'...
$ git fetch origin b09e0027f32fa78d7245e322a57f527eedee0e26:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/glibmm2.4
 * [new ref]         b09e0027f32fa78d7245e322a57f527eedee0e26 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b09e002 Update to 2.66.6