$ git clone -n https://src.fedoraproject.org/rpms/centpkg.git /var/lib/mock/f41-build-side-1-2872640-34370/root/chroot_tmpdir/scmroot/centpkg
Cloning into '/var/lib/mock/f41-build-side-1-2872640-34370/root/chroot_tmpdir/scmroot/centpkg'...
$ git fetch origin 71c56aaf0b8632534eea7d7621a6bc2d82569f39:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/centpkg
 * [new ref]         71c56aaf0b8632534eea7d7621a6bc2d82569f39 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 71c56aa Properly handle non-standard branch names