$ git clone -n https://src.fedoraproject.org/rpms/libserf.git /var/lib/mock/f39-build-2157229-50919/root/chroot_tmpdir/scmroot/libserf
Cloning into '/var/lib/mock/f39-build-2157229-50919/root/chroot_tmpdir/scmroot/libserf'...
$ git fetch origin cf8573cae29cae52ecd6cc7ff2a21faa4b1bc88c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libserf
 * [new ref]         cf8573cae29cae52ecd6cc7ff2a21faa4b1bc88c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at cf8573c Add linking of gssapi to support Kerberos authentication