$ git clone -n https://src.fedoraproject.org/rpms/rebase-helper.git /var/lib/mock/f41-build-side-1-2928559-35091/root/chroot_tmpdir/scmroot/rebase-helper
Cloning into '/var/lib/mock/f41-build-side-1-2928559-35091/root/chroot_tmpdir/scmroot/rebase-helper'...
$ git fetch origin 973c3469c874fe7aaee0d9bc968251ff8c20fa4d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rebase-helper
 * [new ref]         973c3469c874fe7aaee0d9bc968251ff8c20fa4d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 973c346 Update to 0.29.2 upstream release