$ git clone -n https://github.com/xcp-ng-rpms/xs-opam-repo.git /var/lib/mock/v8.3-u-asultanov2-11620-29909/root/chroot_tmpdir/scmroot/xs-opam-repo
Cloning into '/var/lib/mock/v8.3-u-asultanov2-11620-29909/root/chroot_tmpdir/scmroot/xs-opam-repo'...
$ git fetch origin 865aa960fe81a521aca47fb42ddfb47eccba3172:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xs-opam-repo
 * [new ref]         865aa960fe81a521aca47fb42ddfb47eccba3172 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 865aa96 bump release for test build