$ git clone -n https://github.com/xcp-ng-rpms/ipxe /var/lib/mock/v9.0-incoming-11324-29648/root/chroot_tmpdir/scmroot/ipxe
Cloning into '/var/lib/mock/v9.0-incoming-11324-29648/root/chroot_tmpdir/scmroot/ipxe'...
$ git fetch origin 45b05cf5530c53b630f77f19ac86d9c7f2c8d9a1:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/ipxe
 * [new ref]         45b05cf5530c53b630f77f19ac86d9c7f2c8d9a1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 45b05cf Change Requires: perl to perl-interpreter