Use main for Homebrew branches

[MikeMcQuaid]

Verification

• This issue's title and/or description do not reference a single formula e.g. brew install wget. If they do, open an issue at https://github.com/Homebrew/homebrew-core/issues/new/choose instead.

Provide a detailed description of the proposed feature

Homebrew should move to using the now GitHub and Git default of main for our branches.

We should start with less used taps e.g. Homebrew/homebrew-formula-analytics, move to more widely used taps Homebrew/homebrew-services, do so on Homebrew/homebrew-formula-core and Homebrew/homebrew-cask and end with Homebrew/brew.

It will be important to ensure that brew update, brew update-reset and brew test-bot all behave as expected.

What is the motivation for the feature?

Consistency across GitHub.

How will the feature be relevant to at least 90% of Homebrew users?

It's not.

What alternatives to the feature have been considered?

Leaving everything as master.

[gibfahn]

It will be important to ensure that brew update, brew update-reset and brew test-bot all behave as expected.

To confirm, "behave as expected" here means that e.g. brew update will seamlessly move the tap branch from master -> main right? if I recall correctly last time I tried this it instead errored and asked you to run brew tap --repair, which seems like something brew could handle for you.

https://github.com/homebrew/brew/blob/0a358b851875d8fe070396a7870a7f9b0dfc1634/Library/Homebrew/cmd/update-report.rb#L263-L269

[Bo98]

Ideally yeah. And if any fixes are required, it may mean having to keep a copy of master around indefinitely as an intermediate update step.

If it doesn't work well, a local symbolic-ref might be an alternative idea.

[MikeMcQuaid]

To confirm, "behave as expected" here means that e.g. brew update will seamlessly move the tap branch from master -> main right?

Yes.

And if any fixes are required, it may mean having to keep a copy of master around indefinitely as an intermediate update step.

Ideally we don't want to do this but agreed it's worth doing if needed (at least on Homebrew/brew).

[unitof]

In the past, third party taps handled this with opoo but a silent method for renaming the main (or any) branch which doesn't require keeping the old branch around would be welcome.