• Extension version: v0.70.0
• VSCode Version: 1.81.1
• OS: Darwin macOS 13.5.1 (arm64 22.6.0)

Steps to Reproduce:

1. Clone any forked repository via "Clone Git Repository" – "Clone from GitHub" – enter repository URL (this sets up both origin and upstream).
2. Make a small change on a new branch, commit, and publish the branch on origin.
3. Select "Create Pull Request". This will now show the main branch on origin as the base, which is not what I want (since this is a PR of a fork, I want my changes to be merged in upstream).

I know I can select a new base (i.e. upstream/main), but I don't want to do that with every new PR I make. Also, this did work as expected previously, but I cannot pinpoint exactly when this changed.

Another affected behavior: I often use the "Copy GitHub Head Link" functionality (e.g. by right-clicking on a line number). This now also only redirects to the origin repository, whereas I want the link to upstream in almost all cases. This too used to work in some previous version.