$ git clone -n https://src.fedoraproject.org/rpms/emacs.git /var/lib/mock/f41-build-855631-167276/root/chroot_tmpdir/scmroot/emacs
Cloning into '/var/lib/mock/f41-build-855631-167276/root/chroot_tmpdir/scmroot/emacs'...
$ git fetch origin 88b50bfe264b1210bd36b0c9f721fefca106c293:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/emacs
 * [new ref]         88b50bfe264b1210bd36b0c9f721fefca106c293 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 88b50bf Remember to update sources.