$ git clone -n https://github.com/xcp-ng-rpms/xcp-emu-manager.git /var/lib/mock/v8.3-incoming-9932-28628/root/chroot_tmpdir/scmroot/xcp-emu-manager
Cloning into '/var/lib/mock/v8.3-incoming-9932-28628/root/chroot_tmpdir/scmroot/xcp-emu-manager'...
$ git fetch origin c224c5f7ab79b1e458d3a6d7656d141d51959aa6:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xcp-emu-manager
 * [new ref]         c224c5f7ab79b1e458d3a6d7656d141d51959aa6 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c224c5f updated spec + new source