sl pr submit picking upstream over fork is unexpected and not desired

[chipsenkbeil]

I made the mistake of sending a massive number of pull requests to the neovim repository, thinking that sl pr submit --stack would use my fork. I then read through the documentation to realize that it prefers the upstream repository in the case where default or default-push are a fork, which is not the behavior I'd expect.

It's not clear to me how to control this behavior other than not using a forked repository and instead manually cloning the repository using git and pushing to my own version without the fork. As the upstream repository does not want multiple pull requests due to the load on the CI, I was planning to have a dialog on my fork and merge all of the work into a single PR down the line.

Is there any guidance on how to get Sapling's pr submit to go to a fork?