I (and others I assume) would really like to see this in 19;

glancing at the thread above and in the test cases I see this is in good shape for comitter review.

No? 

If I were to add something  it would be an example in copy.sgml 

  <para>
   When the <literal>FORCE_ARRAY</literal> option is enabled,
   the entire output is wrapped in a JSON array and individual rows are separated by commas:
   <programlisting>
COPY (SELECT id, name FROM users) TO STDOUT (FORMAT JSON, FORCE_ARRAY);
   </programlisting>
   <programlisting>
[
{"id": 1, "name": "Alice"}
,{"id": 2, "name": "Bob"}
,{"id": 3, "name": "Charlie"}
]
   </programlisting>
  </para>

Also, apologies if that has been discussed already,

is there a good reason why didn't we just go with a simple "WRAP_ARRAY" ?