$ git clone -n https://src.fedoraproject.org/rpms/matrix-synapse.git /var/lib/mock/f38-build-side-42-init-devel-882100-28486/root/chroot_tmpdir/scmroot/matrix-synapse
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-882100-28486/root/chroot_tmpdir/scmroot/matrix-synapse'...
$ git fetch origin bc09fe417aa8dd3d83c72e9d825af34c8615e65e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/matrix-synapse
 * [new ref]         bc09fe417aa8dd3d83c72e9d825af34c8615e65e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at bc09fe4 Add README.md