$ git clone -n https://src.fedoraproject.org/rpms/R-IRanges.git /var/lib/mock/f42-build-side-110318-58927718-6569309/root/chroot_tmpdir/scmroot/R-IRanges
Cloning into '/var/lib/mock/f42-build-side-110318-58927718-6569309/root/chroot_tmpdir/scmroot/R-IRanges'...
$ git fetch origin e6b384d949a93512e599ae718d3a6d446d2004c1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-IRanges
 * [new ref]         e6b384d949a93512e599ae718d3a6d446d2004c1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e6b384d Update to latest version