$ git clone -n https://github.com/xcp-ng-rpms/trousers.git /var/lib/mock/v8.3-u-pcoval2-10392-28954/root/chroot_tmpdir/scmroot/trousers
Cloning into '/var/lib/mock/v8.3-u-pcoval2-10392-28954/root/chroot_tmpdir/scmroot/trousers'...
$ git fetch origin 8949f0c1325869ff993eb9f3243258d73a0bea40:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/trousers
 * [new ref]         8949f0c1325869ff993eb9f3243258d73a0bea40 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8949f0c bump release for test build