$ git clone -n https://src.fedoraproject.org/rpms/river.git /var/lib/mock/f42-build-side-110464-59017188-6570244/root/chroot_tmpdir/scmroot/river
Cloning into '/var/lib/mock/f42-build-side-110464-59017188-6570244/root/chroot_tmpdir/scmroot/river'...
$ git fetch origin eebd28946c4c63c25dd0057f75187bd42673cd50:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/river
 * [new ref]         eebd28946c4c63c25dd0057f75187bd42673cd50 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at eebd289 Update to 0.3.9 (#2351096)