$ git clone -n https://github.com/xcp-ng-rpms/xen.git /var/lib/mock/v8.3-incoming-10791-29312/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v8.3-incoming-10791-29312/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin 940bb74346778384f88d4e7beb25d6c7aa2a48d8:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         940bb74346778384f88d4e7beb25d6c7aa2a48d8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 940bb74 Merge branch 'XS-8.3' into dnt-XCPNG-2991