$ git clone -n https://src.fedoraproject.org/rpms/river.git /var/lib/mock/f40-build-805128-144696/root/chroot_tmpdir/scmroot/river
Cloning into '/var/lib/mock/f40-build-805128-144696/root/chroot_tmpdir/scmroot/river'...
$ git fetch origin f1eb488a545303ead67f47cf103edf40c68916b0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/river
 * [new ref]         f1eb488a545303ead67f47cf103edf40c68916b0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f1eb488 Upload sources