ci: add ConfigMap-based coverage tracking

[bryan-cox]

Summary

Add coverage comparison using a ConfigMap on the arc-runner-set cluster
to track baseline coverage and report diffs on PRs.

• Extract total and per-directory coverage from cover.out using go tool cover
• On push to main: update a coverage-baseline ConfigMap in arc-runners namespace
• On PRs: compare against baseline at both levels and fail if total coverage drops by more than 1%
• Job summary shows overall trend and a per-directory breakdown with diffs

Depends on: #8060 (Codecov integration)

Setup on runner cluster

The following was applied to the arc-runner-set cluster:

```bash
export KUBECONFIG=/path/to/github-actions-kubeconfig

Create the ConfigMap

kubectl create configmap coverage-baseline -n arc-runners --from-literal=total=0

Grant the runner ServiceAccount access to the ConfigMap

kubectl create role coverage-baseline-access -n arc-runners
--verb=get,patch
--resource=configmaps
--resource-name=coverage-baseline

kubectl create rolebinding coverage-baseline-access -n arc-runners
--role=coverage-baseline-access
--serviceaccount=arc-runners:arc-runner-set-gha-rs-no-permission

Seed with actual baseline (run tests locally and extract coverage):

go test -race -count=1 -timeout=30m ./... -coverprofile cover.out

Build patch with total and per-directory coverage

TOTAL=$(go tool cover -func=cover.out | grep '^total:' | awk '{print $NF}' | tr -d '%')
PATCH="{"data":{"total":"${TOTAL}""
while IFS='=' read -r dir cov; do
PATCH="${PATCH},"dir.${dir}":"${cov}""
done < <(awk '
NR > 1 {
split($1, a, ":"); file = a[1]
sub("github.com/openshift/hypershift/", "", file)
split(file, parts, "/"); dir = parts[1]
stmts = $2; count = $3
total_stmt[dir] += stmts
if (count > 0) covered_stmt[dir] += stmts
}
END {
for (dir in total_stmt)
printf "%s=%.1f\n", dir, (total_stmt[dir] > 0 ? (covered_stmt[dir]/total_stmt[dir])*100 : 0)
}
' cover.out | sort)
PATCH="${PATCH}}}"
kubectl patch configmap coverage-baseline -n arc-runners -p "$PATCH"
```

The workflow updates this ConfigMap automatically on each push to main.

Test plan

• Verify coverage extraction step succeeds on arc-runner-set
• Verify RBAC allows runner SA to access ConfigMap
• Verify baseline ConfigMap seeded with total and per-directory data
• Verify ConfigMap gets updated on push to main
• Verify PR comparison reports diff in job summary with per-directory breakdown

🤖 Generated with Claude Code

[openshift-ci-robot]

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This pull-request has been approved by: bryan-cox

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PR needs rebase.

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[bryan-cox]

/close

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