Lab3 submission

[tdzdslippen]

Goal

Complete Lab 3 — a PR-gated CI pipeline for QuickNotes on GitHub Actions (vet + test + lint), made fast with caching, a Go-version matrix, and path filters.

Changes

• .github/workflows/ci.yml — the pipeline:
  • 3 units: vet, test (go test -race -count=1), lint (golangci-lint pinned v2.5.0); each fails the PR independently.
  • Pinned runtime: ubuntu-24.04 everywhere (no :latest).
  • Supply-chain hardening: every third-party action pinned by full 40-char commit SHA (checkout v4.2.2, setup-go v5.6.0, golangci-lint-action v8.0.0), permissions: contents: read (least privilege).
  • Speed (Task 2): setup-go build/module cache keyed on go.mod (no go.sum — std-lib only); strategy.matrix over Go 1.23 + 1.24 with fail-fast: false; paths: filter so docs-only PRs don't run CI.
  • ci-gate aggregate job → a single stable required status check for branch protection.
• submissions/lab3.md — full write-up: requirements mapping, real run links + timings, the deliberate-failure/fix evidence, branch-protection screenshots (§1.7), and written answers to all 8 design questions (a–h) + bonus bottleneck analysis.
• submissions/branch-protection-*.png — branch-protection rule on main (required check ci-gate).

Testing

• Green pipeline (cache + matrix), 37 s wall-clock: https://github.com/tdzdslippen/DevOps-Intro/actions/runs/27506521594
• Gate blocks a deliberately broken test (TestHealth_ReportsCount, commit 2e38db9): both test legs + ci-gate red → PR cannot merge: https://github.com/tdzdslippen/DevOps-Intro/actions/runs/27506990278
• Green again after revert (bf66572): https://github.com/tdzdslippen/DevOps-Intro/actions/runs/27507029572
• Branch protection on main requires ci-gate; a --force-with-lease to main was rejected with protected branch hook declined.
• Timing table (real runs): baseline single/no-cache 39 s · +cache 35 s · cache+matrix 37 s · cold cache 45 s.

Checklist

• Title is a clear sentence (≤ 70 chars)
• Commits are signed (git log --show-signature)
• submissions/labN.md updated