$ git clone -n https://src.fedoraproject.org/rpms/ceph.git /var/lib/mock/f41-build-side-1-2882818-34495/root/chroot_tmpdir/scmroot/ceph
Cloning into '/var/lib/mock/f41-build-side-1-2882818-34495/root/chroot_tmpdir/scmroot/ceph'...
remote: warning: refname 'HEAD' is ambiguous.        
$ git fetch origin 571002cfed7a641872369bb12b0fd767bb3e2123:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ceph
 * [new ref]         571002cfed7a641872369bb12b0fd767bb3e2123 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 571002c Merge remote-tracking branch 'origin' into f41