update the name of the main branch

[bnord]

Describe the bug
"Master" harkens a racist heritage and vocabulary. Could we change the name to 'Main' or something else?

Expected behavior
here's a way to do that: https://jarv.is/notes/github-rename-master/

[ntessore]

here is what needs changing — I don't think this is a problem for the contributors, everyone will need to checkout main and branch off from there for their next feature branch

[rrjbca]

Very happy with this suggestion. main is the new GH default so lets stick with that. Three things I can think of that also need updating:

• Branch protection rules
• Update base branch for open PRs
• Default branch for third party integrations (codecov, readthedocs)

I'm happy to address this and would suggest the following (probably overly cautious) approach to prevent anything going wrong with our open PRs (which we have seen before):

• Open a new PR with the changes outlined by @ntessore using master as the base (Update name of default branch to main #434)
• Create and push the new main branch as outlined by @bnord
• Apply the same branch protections from master to main (change the branch name pattern to ma*)
• Change the base branch for the PR in the first step to main and merge it
• Change the base branch for all other open PRs to main
• Change the default branch on codecov and readthedocs to main
• Change the default branch on GitHub to main and delete master
• Delete the master branch on GitHub
• Change the branch protection name pattern to main

[CKrawczyk]

Any github actions that run on PR/merge into master will also need to be updated to main.

[rrjbca]

I believe most of the work required has been completed. @skypyproject/skypy-infrastructure @skypyproject/skypy-board would somebody please check the following before I go ahead with the final changes:

• https://github.com/skypyproject/skypy/pulls the base branch for all PRs is skypyproject/main
• https://skypy.readthedocs.io/en/latest/developer/contributing.html refers to the new main branch

[ntessore]

looks good to me, and if anything slips through it should not be difficult to fix it

[Lucia-Fonseca]

Looks good to me too.

[rrjbca]

Thanks, I have updated the default branch to main. I will wait for a short time (~1 week) before deleting master and closing this issue in case any unforeseen problems arise.

[rrjbca]

The switch to main as the new default branch has not encountered any issues so far. I have therefore deleted master and updated the branch protection rules. Closing.