$ git clone -n https://github.com/xcp-ng-rpms/opam.git /var/lib/mock/v8.3-u-psafont2-9742-28450/root/chroot_tmpdir/scmroot/opam
Cloning into '/var/lib/mock/v8.3-u-psafont2-9742-28450/root/chroot_tmpdir/scmroot/opam'...
$ git fetch origin 9706d0e2de764888b7d96878ce06f36fcb483bec:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/opam
 * [new ref]         9706d0e2de764888b7d96878ce06f36fcb483bec -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 9706d0e bump release for test build