$ git clone -n https://github.com/xcp-ng-rpms/dummypkg.git /var/lib/mock/v8.3-u-stormi1-9426-28171/root/chroot_tmpdir/scmroot/dummypkg
Cloning into '/var/lib/mock/v8.3-u-stormi1-9426-28171/root/chroot_tmpdir/scmroot/dummypkg'...
$ git fetch origin 1cdb69ef66508a881674a00f2b34aae7d60c9ffc:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/dummypkg
 * [new ref]         1cdb69ef66508a881674a00f2b34aae7d60c9ffc -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1cdb69e bump release for test build