Determine whether automerging can be made to work when fork branches are behind as well as ahead of main

[dylanhmorris]

If not, add guidance to make sure branch is strictly ahead of main for PR automerge

Compare:
https://github.com/CDCgov/covid19-forecast-hub/actions/runs/11945156368 (failed)
https://github.com/CDCgov/covid19-forecast-hub/actions/runs/11945068385 (succeeded)

[sbidari]

I have not found a way to make automerge work when fork branches are behind main, I can look into it more but I think the easiest thing to do at least for now is enable Always suggest updating pull request branches in the repo settings which will suggest teams to sync their branch with main if it's behind.

[dylanhmorris]

Makes sense. I would also add a note to the documentation in the same area as the bit on automerging

[dylanhmorris]

@sbidari added notes in #87. I think we should keep this open for a little while to explore whether things can work more automatically with reconcilable (but divergent) branches.

[sbidari]

I agree!