chore: Rename default branch from master to main

[lykinsbd]

Problem

The default branch is named master, which does not match modern conventions. GitHub now defaults to main for new repositories, and most Go projects and tooling expect main.

Steps

1. Rename the branch on GitHub: Settings → Branches → Rename master to main
2. Update local checkouts: git branch -m master main && git fetch origin && git branch -u origin/main main
3. Update hardcoded references in the repo:
   • .github/workflows/test.yml: git-token: ${{ github.ref_name == 'master' && ... }} → main
   • README.md: badge URL ...badges/.badges/master/coverage.svg → ...badges/.badges/main/coverage.svg
   • .goreleaser.yml: verify no hardcoded branch references
4. Rename the badge path on the badges branch: move .badges/master/ → .badges/main/
5. Update the fgrosse/go-coverage-report baseline lookup — it searches for artifacts from the master branch push workflow; this will update automatically once the branch is renamed

Notes

GitHub will automatically redirect master → main for existing clone URLs, so existing users will not be broken immediately. The redirect is not permanent — users should update their remotes.

[lykinsbd]

@tbotnz — all the file changes are done and merged to master (workflow condition, README badge URL, badge SVG path on the badges branch). The only remaining step requires repo admin access:

Settings → Branches → rename master to main

Once that's done, local checkouts just need:

git branch -m master main
git fetch origin
git branch -u origin/main main

No rush — everything is backward-compatible until the rename happens.

[lykinsbd]

Updated: What needs changing when we rename master → main

PR #142 fixed all premature main references back to master so things actually work. When we're ready to do the rename, here's the complete checklist:

GitHub Settings (requires admin)

• Settings → Branches → Rename master to main

Files to update (master → main)

• .github/workflows/test.yml — git-token condition: github.ref_name == 'master' → 'main'
• .github/workflows/docs.yml — branch trigger: branches: [master] → [main]
• CONTRIBUTING.md — branch instructions (lines 20, 24)
• docs/contributing.md — branch instructions (lines 20, 24)
• README.md — coverage badge URL: .badges/master/ → .badges/main/
• docs/index.md — coverage badge URL + LICENSE link

Badges branch

• Rename .badges/master/ → .badges/main/ on the badges branch

Post-rename

• Verify CI runs on push to main
• Verify docs deploy triggers on push to main
• Verify coverage badge updates correctly

Notes

• .goreleaser.yml references to main are Go package names, not branch — no change needed
• CHANGELOG.md references are historical — no change needed
• GitHub auto-redirects old master URLs temporarily, but contributors should update remotes