community/github-management/default-branch-migration.md

title	linkTitle	description	weight	type	aliases
Default Branch Migration	Default Branch Migration	Instructions on how to migrate the default branch from master to main.	99	docs	/rename

Default Branch Migration

This document outlines steps needed to migrate the default branch of your repo from master to main.

Note: This document is currently a work in progress.

If you have questions about the process, reach out to the GitHub Management Team on the #github-management channel on slack or open an issue in the kubernetes/org repo.

Prerequisites

• Create an issue in your repo to track the branch rename. You can paste this checklist in the issue body.

• If you are not a root approver for the repo, assign a root approver for approval.

• Once the issue has been approved, send a notice to your SIG's mailing list about the potential branch rename.

Changes pre-rename

Make the following changes before renaming the branch the master branch.

Note: There might be additional changes required that have not been covered in this checklist.

Note: There might be additional information available in the umbrella issue via [kubernetes/org#2222].

Anytime

These changes are non-disruptive and can be made anytime before renaming the branch.

• If a presubmit or postsubmit prowjob triggers on the master branch (branches field of the prowjob), add the main branch to the list (see kubernetes/test-infra#20665 for an example).

• If the milestone_applier prow config references the master branch, add the main branch to the config (see kubernetes/test-infra#20675 for an example).

• If the branch_protection prow config references the master branch, add the main branch to the config.

Just before rename

These changes are disruptive and should be made just before renaming the branch.

• For periodic prowjobs, or any prowjob that mentions the master branch in base_ref, update them to the main branch. Ensure that these changes happen in lock-step with the branch rename (jobs triggered in between landing these changes and renaming the branch will fail).

  • For bootstrap-based jobs, ensure the branch is explicitly specified, e.g. kubernetes/foo=main. kubernetes/test-infra#20667 may eventually allow for non-disruptive changes.
  • For pod-utils based jobs, ensure the branch is explicitly specified, e.g. base_ref: main. kubernetes/test-infra#20672 may eventually allow for non-disruptive changes.

• If a prowjob mentions master in its name, rename the job to not include the branch name, e.g. pull-repo-verify-master -> pull-repo-verify. status-reconciler should automatically migrate PR status contexts to the new job name, and retrigger accordingly, but we have anecdotally found it sometimes misses changes.

  • NOTE: our infrastructure doesn't understand the concept of job renames, so from the perspective of e.g. https://testgrid.k8s.io the job will appear to have lost history and start from scratch.

• If a prowjob calls scripts or code in your repo that explicitly reference master, update all references to use main, or auto-detect the remote branch

  • e.g. using git to auto-detect

  # for existing clones, update their view of the remote
  git fetch origin
  git remote set-head origin -a
  # for new clones, or those updated as above, this prints "main" post-rename
  echo $(git symbolic-ref refs/remotes/origin/HEAD)
  

  • e.g. using github's api to auto-detect

  # gh is https://github.com/cli/cli, this will print "main" post-rename
  gh api /repos/kubernetes-sigs/slack-infra | jq -r .default_branch
  

• If the repo has netlify configured for it, ask a member of the GitHub Management Team to rename the master branch to main in the netlify site config. It can't be controlled through the netlify config in the repo.

Approval

• Once all non-disruptive tasks have been completed and disruptive tasks have been identified, assign the GitHub Management team (@kubernetes/owners) for approval.

Rename the default branch

• Rename the default branch from master to main using the GitHub UI by following the official instructions.

Changes post-rename

After the default branch has been renamed to main, make the following changes.

Note: There might be additional changes required that have not been covered in this checklist.

Prowjobs

• If a prowjob still references the master branch in the branches field, remove the master branch (see kubernetes/test-infra#20669 for an example).

Prow config

• If the milestone_applier prow config references the master branch, remove it from the config.

• If the branch_protection prow config references the master branch, remove it from the config.

Other

• If any docs reference the master branch, update to main (URLs will be automatically redirected).

• Ensure that CI and PR tests work fine.

  • If there are any outstanding PRs you can /approve to merge, do so to verify that presubmits and postsubmits work as expected

• Trial the local development experience with a pre-rename clone.

  • ensure Github instructions to rename your local branch work
  • consider updating your fork's default remote branch name such that if you have git autocompletion enabled, typing ma<tab> will autocomplete to main

• Send a notice about the branch rename to your SIG's mailing list. Include the link to the GitHub instructions to rename your local branch.