$ git clone -n https://src.fedoraproject.org/rpms/nanopb.git /var/lib/mock/f38-build-side-42-init-devel-1082696-29834/root/chroot_tmpdir/scmroot/nanopb
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-1082696-29834/root/chroot_tmpdir/scmroot/nanopb'...
$ git fetch origin 921442f5ff94b24617eb543ce0e95f2545cce96b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/nanopb
 * [new ref]         921442f5ff94b24617eb543ce0e95f2545cce96b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 921442f initial import; rhbz#2216595