$ git clone -n https://src.fedoraproject.org/rpms/R-snow.git /var/lib/mock/f42-build-side-1-3498659-45963/root/chroot_tmpdir/scmroot/R-snow
Cloning into '/var/lib/mock/f42-build-side-1-3498659-45963/root/chroot_tmpdir/scmroot/R-snow'...
$ git fetch origin 7097eff53fbc7c2d8483445f06a46ae62c5aa8b1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-snow
 * [new ref]         7097eff53fbc7c2d8483445f06a46ae62c5aa8b1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7097eff R-maint-sig mass rebuild