$ git clone -n https://src.fedoraproject.org/rpms/mupdf.git /var/lib/mock/f40-build-2012203-45775/root/chroot_tmpdir/scmroot/mupdf
Cloning into '/var/lib/mock/f40-build-2012203-45775/root/chroot_tmpdir/scmroot/mupdf'...
$ git fetch origin effcc4c06a13df8a78be5e34e04f4fc7fe19c11b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mupdf
 * [new ref]         effcc4c06a13df8a78be5e34e04f4fc7fe19c11b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at effcc4c rebase to 1.23.5 (rhbz#2243150)