$ git clone -n https://src.fedoraproject.org/rpms/golang-gopkg-mgo-2.git /var/lib/mock/f41-build-1036599-18741/root/chroot_tmpdir/scmroot/golang-gopkg-mgo-2
Cloning into '/var/lib/mock/f41-build-1036599-18741/root/chroot_tmpdir/scmroot/golang-gopkg-mgo-2'...
$ git fetch origin 2658ce7be22ab07de022e4e5eebe6b3e2e62da29:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/golang-gopkg-mgo-2
 * [new ref]         2658ce7be22ab07de022e4e5eebe6b3e2e62da29 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 2658ce7 Fix FTBFS