$ git clone -n https://github.com/xcp-ng-rpms/trousers.git /var/lib/mock/v8.3-u-pcoval2-10561-29116/root/chroot_tmpdir/scmroot/trousers
Cloning into '/var/lib/mock/v8.3-u-pcoval2-10561-29116/root/chroot_tmpdir/scmroot/trousers'...
$ git fetch origin 3b1aad41a19a5cce16d831678572c3b22cec1d2b:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/trousers
 * [new ref]         3b1aad41a19a5cce16d831678572c3b22cec1d2b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3b1aad4 bump release for test build