$ git clone -n https://github.com/xcp-ng-rpms/xs-opam-repo.git /var/lib/mock/v8.3-u-asultanov2-9198-27999/root/chroot_tmpdir/scmroot/xs-opam-repo
Cloning into '/var/lib/mock/v8.3-u-asultanov2-9198-27999/root/chroot_tmpdir/scmroot/xs-opam-repo'...
$ git fetch origin 29744e5e2339b2ef3f57ecf6a22d0e3f7d2d40c0:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xs-opam-repo
 * [new ref]         29744e5e2339b2ef3f57ecf6a22d0e3f7d2d40c0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 29744e5 bump release for test build