Rename "master" branch to "main"

[mboersma]

There has been an effort to use a friendlier name for the main branch of Kubernetes projects (and others), but image-builder doesn't yet. We should investigate the steps involved and the possible problems this creates, then make a plan to do it. We should also think about how to coordinate this with the "cruft removal" work in #1143.

See discussion at #1160 (comment).

[jsturtevant]

There is some guidance in https://www.kubernetes.dev/resources/rename/

[AverageMarcus]

Collecting some things we'll need to update based on the docs link @jsturtevant shared:

• References to master branch when image-builder defined as an extra_ref - https://github.com/search?q=repo%3Akubernetes%2Ftest-infra%20sigs.k8s.io%2Fimage-builder&type=code
• Update cron trigger to also include main branch - https://github.com/kubernetes-sigs/image-builder/blob/ab5746d83266863140e9974f20e0509f4d38ce82/images/capi/packer/azure/.pipelines/smoke-test.yaml#LL21C1-L21C1

So far, besides those two, I can't find any more references specifically to the master branch.

[jsturtevant]

We will need to update test-infra CI references as well:

• https://github.com/kubernetes/test-infra/tree/master/config/jobs/kubernetes-sigs/image-builder

[AverageMarcus]

@jsturtevant where do those reference the master branch?

[jsturtevant]

looking closer, it does appear to have branch names in those files. so we should be ok 👍

[AverageMarcus]

This is copied from https://www.kubernetes.dev/resources/rename/ so we can track progress in here. :) @mboersma Not sure if you want to copy this into the main body of the issue or not.

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.

[AverageMarcus]

(I've pulled out the outstanding tasks from above so its more easily readable)

ToDo

Before Rename

• Rename image-builder default branch to main kubernetes/test-infra#29671 (currently waiting on approval from CAPI provider maintainers)
• Post message to SIG mailing list about - an initial message was sent along with the "cruft removal" but it might be good to have a standalone post
• Ask a member of the GitHub Management Team to rename the master branch to main in the netlify site config.

During Rename

• Post a message in #image-builder slack channel announcing the rename is underway
• Rename the default branch from master to main using the GitHub UI by following the official instructions.

After Rename

• /unhold Rename image-builder default branch to main kubernetes/test-infra#29671
• /unhold Update main branch referenced in docs #1203
• Check CI jobs still work
• Announce completion of rename to SIG mailing list and #image-builder Slack channel

[palnabarun]

I have updated the Netlify production branch to main and triggered a deployment to test the change. We are ✅.

[AverageMarcus]

All complete and everything looks to be working. Thanks everyone! 🎉

/close

[k8s-ci-robot]

@AverageMarcus: Closing this issue.

In response to this:

All complete and everything looks to be working. Thanks everyone! 🎉

/close

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