$ git clone -n https://github.com/xcp-ng-rpms/xcp-emu-manager.git /var/lib/mock/v8.3-incoming-9928-28628/root/chroot_tmpdir/scmroot/xcp-emu-manager
Cloning into '/var/lib/mock/v8.3-incoming-9928-28628/root/chroot_tmpdir/scmroot/xcp-emu-manager'...
$ git fetch origin b32793d00784209e5ba2e0b7498c60120ddc349d:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xcp-emu-manager
 * [new ref]         b32793d00784209e5ba2e0b7498c60120ddc349d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b32793d updated spec + new source