"I imagine there's a more elegant way to do this using a window function"

[curiousleo]

https://til.simonwillison.net/sql/cumulative-total-over-time says:

I imagine there's a more elegant way to do this using a window function but this works fine.

I was looking at queries of this sort recently. Here would be my suggestion:

select
  created_at,
  count(*) over (
    order by
      created_at
  ) as cumulative
from
  repos
where
  "owner" = :owner
order by
  created_at desc

It seems to run a little faster than the original query too.

Example query

I'd have written you an e-mail but couldn't find one on your website.