prep kubernetes/org jobs for default branch rename

[spiffxp]

specificalky

• add main to any pre/postsubmit triggers that reference master
• try removing explicit master base_ref, see if that gets us default branch

Part of kubernetes/org#2466

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[spiffxp]

My read of the clone part of pod-utils is that they assume base_ref is present.

test-infra/prow/pod-utils/clone/clone.go

Lines 203 to 229 in 94c2ba7

	if !refs.SkipFetchHead {
	fetchArgs := []string{g.repositoryURI, "--tags", "--prune"}
	fetchArgs = append(fetchArgs, depthArgs...)
	commands = append(commands, g.gitFetch(fetchArgs...))
	}
	{
	fetchArgs := append([]string{}, depthArgs...)
	fetchArgs = append(fetchArgs, g.repositoryURI, refs.BaseRef)
	commands = append(commands, g.gitFetch(fetchArgs...))
	}
	var target string
	if refs.BaseSHA != "" {
	target = refs.BaseSHA
	} else {
	target = "FETCH_HEAD"
	}
	// we need to be "on" the target branch after the sync
	// so we need to set the branch to point to the base ref,
	// but we cannot update a branch we are on, so in case we
	// are on the branch we are syncing, we check out the SHA
	// first and reset the branch second, then check out the
	// branch we just reset to be in the correct final state
	commands = append(commands, g.gitCommand("checkout", target))
	commands = append(commands, g.gitCommand("branch", "--force", refs.BaseRef, target))
	commands = append(commands, g.gitCommand("checkout", refs.BaseRef))

It's not clear to me whether something further up the stack does something to default base_ref if not set.

Locally

• git fetch origin '' is equivalent to fetching all branches, and git checkout FETCH_HEAD puts me on whichever branch was alphabetically first
• git branch --force "" FETCH_HEAD errors with fatal: '' is not a valid branch name.

Tests are happy though!

[spiffxp]

For purposes of migrating kubernetes/org today, I'm going to defer further experiments on making periodics resilient to remote branch renames to a job that runs more frequently than 24h. EDIT: opened #20667 for further exploration

Putting the base_ref back...

[spiffxp]

/cc @mrbobbytables

[mrbobbytables]

/lgtm

[k8s-ci-robot]

@spiffxp: Updated the job-config configmap in namespace default at cluster test-infra-trusted using the following files:

• key test-infra-trusted.yaml using file config/jobs/kubernetes/test-infra/test-infra-trusted.yaml

In response to this:

specificalky

• add main to any pre/postsubmit triggers that reference master
• try removing explicit master base_ref, see if that gets us default branch

Part of kubernetes/org#2466

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