$ git clone -n https://src.fedoraproject.org/rpms/R-widgetTools.git /var/lib/mock/f42-build-side-110318-58927028-6569309/root/chroot_tmpdir/scmroot/R-widgetTools
Cloning into '/var/lib/mock/f42-build-side-110318-58927028-6569309/root/chroot_tmpdir/scmroot/R-widgetTools'...
$ git fetch origin 0bc42144747a8a3655ca8d2e921ec1e09adf641a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-widgetTools
 * [new ref]         0bc42144747a8a3655ca8d2e921ec1e09adf641a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0bc4214 R-maint-sig mass rebuild