Rename primary branch to “main”

[j9t]

After CSS N/D 2025, I suggest we rename the primary branch to “main.”

We should check on existing PRs, but if there isn’t anything critical, the change is usually straightforward.

[arkhi]

Sure.

I have nothing against as long as little adjustments don’t cause extra work down the line.

I’m wondering if we should not do this when the website is being rebuilt though. master could then be renamed to something meaningful like legacy or such.