Action fails due to "HttpError: There are merge conflicts"

[matchai]

Hi there,

Thank you for your excellent action, Mislav. We've been using it as part of our release process over at https://github.com/starship/starship for a while now.

With the latest release of the action, we started seeing a strange failure with the following error:

POST /repos/Homebrew/homebrew-core/forks - 202 in 316ms
POST /repos/matchai/homebrew-core/merge-upstream - 409 in 1071ms
Error: HttpError: There are merge conflicts

Full logs: https://github.com/starship/starship/runs/4599656801?check_suite_focus=true#step:2:17

[mislav]

@matchai Thank you for reporting. I'll try to address this, but in the meantime, the workaround would be to drop down to git, check out the default branch of matchai/homebrew-core, hard-reset it to the latest state of the default branch in upstream, and force-push that to your fork. The idea is that the default branch in your fork always tracks the latest state in upstream, but that can't happen if the branch in your fork has diverged for some reason.