$ git clone -n https://github.com/xcp-ng-rpms/xcp-emu-manager.git /var/lib/mock/v8.3-incoming-9943-28628/root/chroot_tmpdir/scmroot/xcp-emu-manager
Cloning into '/var/lib/mock/v8.3-incoming-9943-28628/root/chroot_tmpdir/scmroot/xcp-emu-manager'...
$ git fetch origin fc6438da1d996b615c4f124b313aa0a6840c71f2:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xcp-emu-manager
 * [new ref]         fc6438da1d996b615c4f124b313aa0a6840c71f2 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fc6438d updated spec + new source