$ git clone -n https://src.fedoraproject.org/rpms/R-poLCA.git /var/lib/mock/f42-build-side-1-3501320-45974/root/chroot_tmpdir/scmroot/R-poLCA
Cloning into '/var/lib/mock/f42-build-side-1-3501320-45974/root/chroot_tmpdir/scmroot/R-poLCA'...
$ git fetch origin 37d787a89b0ffa5e323af6633c154191f05d3e8c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-poLCA
 * [new ref]         37d787a89b0ffa5e323af6633c154191f05d3e8c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 37d787a R-maint-sig mass rebuild