Rename default branch for kubernetes/org

[spiffxp]

Part of umbrella issue https://github.com/kubernetes/org/issues/2222

Issue to spec out and then run through renaming the default branch for this repository

• update pre/postsubmits to trigger on old branch name and new branch name
• determine whether periodics use default branch or have name hardcoded in git commands
  • if hardcoded, does attempting to checkout old name break?
• determine whether branch name is part of any job names
• determine if any docs need to be updated
• send notice
• rename branch (ref: https://github.com/github/renaming#renaming-existing-branches)
• if necessary, update periodics to refer to new branch name
• if necessary, rename jobs
• update branch protection config
• update jobs to only trigger on new branch name
• make sure things still work
  • keep an eye on ci and prs for a bit
  • trial the local development experience with pre-rename clone
• send notice

/sig contributor-experience /area github-management owns the repo /sig testing to discover any prow issues /milestone v1.21 /priority important-soon /assign @spiffxp I plan on working through this

[k8s-ci-robot]

@spiffxp: The provided milestone is not valid for this repository. Milestones in this repository: [v1.19, v1.20]

Use /milestone clear to clear the milestone.

In response to [this](https://github.com/kubernetes/org/issues/2466): >Issue to spec out and then run through renaming the default branch for this repository > >- update pre/postsubmits to trigger on old branch name and new branch name >- determine whether periodics use default branch or have name hardcoded in git commands > - if hardcoded, does attempting to checkout old name break? >- determine whether branch name is part of any job names >- determine if any docs need to be updated >- send notice >- rename branch (ref: https://github.com/github/renaming#renaming-existing-branches) >- if necessary, update periodics to refer to new branch name >- if necessary, rename jobs >- update branch protection config >- update jobs to only trigger on new branch name >- make sure things still work > - keep an eye on ci and prs for a bit > - trial the local development experience with pre-rename clone >- send notice > >/sig contributor-experience >/area github-management >owns the repo >/sig testing >to discover any prow issues >/milestone v1.21 >/priority important-soon >/assign @spiffxp >I plan on working through this Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.

[spiffxp]

/milestone v1.21

[spiffxp]

prowjob configs:

• presubmits: don't explicitly mention master -> do nothing, should work fine post-rename
• postsubmits: trigger on master -> add main, remove master post-rename
• periodics: ci-org-peribolos uses pod-utils to explicitly clone master branch -> must merge a PR to switch, either pre or post-rename
• PR for prep: https://github.com/kubernetes/test-infra/pull/20665

prowjob names:

• master isn't in their names

prowjob contents:

• kubernetes/org doesn't contain reference to 'master' in its codebase

prow configs:

• plugins:
  • slack: repo is mentioned explicitly, but branch name is not (actually no repo mentions it, so probably don't need to check going forward)
  • repo_milestone: repo is mentioned explicitly, but /milestone doesn't depend on branchnn
  • milestone_applier: I'm going to add this to see how it behaves
• configs:
  • branch_protector: repo is mentioned explicitly, but branch name is not
• PR for prep: https://github.com/kubernetes/test-infra/pull/20664

docs:

• cs.k8s.io shows some links with branch in their uri, but github should handle redirecting these post-rename

[spiffxp]

OK I'm going to click the button...

[justaugustus]

Do itttttt 🎉 ✨ /pony party

[k8s-ci-robot]

@justaugustus:

In response to [this](https://github.com/kubernetes/org/issues/2466#issuecomment-770006709): >Do itttttt 🎉 ✨ >/pony party Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.

[spiffxp]

Pushed the button.

Slack alerter fired:

presubmits for open PRs and postsubmits were retriggered:

visiting the repo via the website now shows a popup

[spiffxp]

Doing a PR via the UI already uses the correct branch name. I happen to use hub pull-request a lot locally, let me see what that experience is like...

trying hub pull-request from a local copy of the repo that hasn't been updated at all:

$ hub pull-request
Error creating pull request: Unprocessable Entity (HTTP 422)
Invalid value for "base"

trying git fetch from a local copy of the repo that hasn't been updated at all

$ git fetch origin master
fatal: couldn't find remote ref master

updated per their instructions

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

hub pull-request still not working...

Fetch origin as I usually do...

$ git fetch --prune origin
From github.com:kubernetes/org
 - [deleted]           (none)     -> origin/master
   (refs/remotes/origin/HEAD has become dangling)

dangling you say?

$ cat .git/refs/remotes/origin/HEAD
ref: refs/remotes/origin/master

let's update that

$ git remote set-head origin -a
origin/HEAD set to main

hub pull-request works now, yay

[spiffxp]

Sample PR to confirm things still work (without a post-rename PR yet): https://github.com/kubernetes/org/pull/2473

[mrbobbytables]

The pre/post submits getting re-triggered for smaller repos will probably be fine, but I fear what it'd do for k/k 😬

[spiffxp]

Yeah once I wrap this up I'd like to writeup where we got lucky and what we should watch out for to help choose other candidates and identify blockers/mitigations

[spiffxp]

Post-rename cleanup PR merged: https://github.com/kubernetes/test-infra/pull/20669

[spiffxp]

Notice sent to https://groups.google.com/g/kubernetes-dev/c/mKwxJW5z2Lk

[spiffxp]

Where we got lucky:

• few open PRs; we didn't have to mitigate a huge spike in CI load
• infrequent periodics; we didn't have to mitigate periodics breaking pre-rename or post-rename
• master not in job names; we didn't have to deal with status-context renames or loss of testgrid history
• jobs didn't explicitly reference master in their code

Lessons learned:

• the only plugin config that explicitly lists master is milestone_applier - try adding both branches pre-rename
• the only prow config that explicitly lists master is branch-protection (for kubernetes/website)
• the branch rename looks like a delete/create via the API
• as expected, all presubmits/postsubmits get re-triggered
• I found I needed to use git remote origin set-head -a for my local clone, in addition to the instructions GitHub provided

Some mitigations to consider:

• adding master/main preemptively to presubmits/postsubmits could probably be scripted well ahead of time
• if we want periodics to support the idea of "use the default branch" so they don't need to be updated pre/post-rename...
  • pod-utils needs to be updated, currently requires hardcoded branch (ref: https://github.com/kubernetes/test-infra/issues/20667)
  • bootstrap needs to be updated, assumes master if branch omitted (ref: https://github.com/kubernetes/test-infra/issues/20672)
• prow can throttle how many of a given job can run with max_concurrency, but I suspect a large enough flood of pending jobs will timeout before they are all processed

[spiffxp]

I'm holding this open until we see the next run of https://testgrid.k8s.io/sig-contribex-org#ci-peribolos to confirm it's using the new branch

[spiffxp]

/close Next run passed, confirmed using main https://prow.k8s.io/view/gcs/kubernetes-jenkins/logs/ci-org-peribolos/1355356401299361792

[k8s-ci-robot]

@spiffxp: Closing this issue.

In response to [this](https://github.com/kubernetes/org/issues/2466#issuecomment-770245483): >/close >Next run passed, confirmed using main https://prow.k8s.io/view/gcs/kubernetes-jenkins/logs/ci-org-peribolos/1355356401299361792 Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.