cluster on table rewrite

I need to add a new column to my largest table, something like:

alter table foo add column col_15 text not null default 'foobar';

I am tempted to add the column as NULL, and then use coalesce and nullif in
the client code to re-interpret NULL as being the value 'foobar'. But I
think that that would be penny wise and pound foolish, so am willing to
bite the bullet of doing a table rewrite.

But while I am rewriting it anyway, is there a way to get it to re-CLUSTER
on the cluster index, as one operation? The rewrite caused by the ADD
COLUMN doesn't automatically cluster.

The closest I can hit upon is to do something like:

create table foo_new as select *, 'foobar'::text as col_15 from foo order
by col_8;

But then I have to manually juggle renaming tables and foreign key
constraints and such.

Is there a better way?

Cheers,

Jeff