$ git clone -n https://src.fedoraproject.org/rpms/mpfr.git /var/lib/mock/f41-build-772588-13506/root/chroot_tmpdir/scmroot/mpfr
Cloning into '/var/lib/mock/f41-build-772588-13506/root/chroot_tmpdir/scmroot/mpfr'...
$ git fetch origin 45cb3e8d14427f36952a17f37ecd153c1830da7c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mpfr
 * [new ref]         45cb3e8d14427f36952a17f37ecd153c1830da7c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 45cb3e8 Own the documentation directory (bz 2279758)