So, you probably saw that checkmark on the GitHub repository settings page: "Require a pull request before merging". Today I learnt, it's quite a literal statement. After you open a PR, you can just push to the branch the same commit and GitHub allows you to do so. 🤪

Found out because I mistyped origin to upstream and it happily merged my PR. Even weirder, I attempted to push 2 commits. One was in the PR, that ended up on main. The other was not, that simply went missing, with git reporting the head the same. Strange shit going on in there.