$ git clone -n https://src.fedoraproject.org/rpms/nanopb.git /var/lib/mock/f39-build-1818509-41839/root/chroot_tmpdir/scmroot/nanopb
Cloning into '/var/lib/mock/f39-build-1818509-41839/root/chroot_tmpdir/scmroot/nanopb'...
$ git fetch origin e21fe6a190a8ef92e124242aacb6e20653552b68:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/nanopb
 * [new ref]         e21fe6a190a8ef92e124242aacb6e20653552b68 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e21fe6a update to 0.4.8