$ git clone -n https://src.fedoraproject.org/rpms/csdiff.git /var/lib/mock/f41-build-side-1-2749955-31015/root/chroot_tmpdir/scmroot/csdiff
Cloning into '/var/lib/mock/f41-build-side-1-2749955-31015/root/chroot_tmpdir/scmroot/csdiff'...
$ git fetch origin abf9a033aa5789c8058577ee3a6c39ce25731220:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/csdiff
 * [new ref]         abf9a033aa5789c8058577ee3a6c39ce25731220 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at abf9a03 update to latest upstream (3.5.1)