Cancel superseded CI runs and skip image builds PRs cannot affect

[f213]

Motivation

Modern agent-driven development ("vibe-coding") produces many PRs, and CI minutes scale with them: in zoya, a production project running this template's CI shape, GitHub Actions alone began costing ~$100/month. The two biggest line items were superseded runs of the same PR completing pointlessly, and every PR building all three Docker images even when nothing image-affecting changed. This PR ports both cost guards from zoya's CI.

Concurrency guard (both workflows)

Both the template repo's own .github/workflows/ci.yml and the workflow generated projects inherit get a top-level concurrency group keyed on workflow and ref:

concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: ${{ github.event_name == 'pull_request' }}

Pushing a new revision to a PR cancels the now-obsolete run of the previous one. cancel-in-progress is conditional on the event, so a push to master is never cancelled — every master run completes.

Conditional image build (generated project's workflow)

The lint job gains a step, run only on pull requests, that lists the PR's changed files via the GitHub API and checks them against the set that can affect the image build: Dockerfile, uv.lock, pyproject.toml, .dockerignore. The verdict is exposed as a job output, and build-docker-image now skips when a PR touches none of those files:

needs: [lint, test]
if: github.event_name != 'pull_request' || needs.lint.outputs.image-build-affected == 'true'

Adding lint to needs is required to read the output; execution order is unchanged since test already needs lint. Pushes to master always build all three images — the condition only ever skips PR runs.

The generated workflow lives under _copy_without_render in cookiecutter.json, so the added ${{ }} expressions pass through cookiecutter untouched.

🤖 Generated with Claude Code

[f213]

Если ни у кого нет возражений, я смёрджу

[nvo87]

да, круто. Мы до этого у себя билд образа делали опциональным. И при авто-мердже, в пулл-реквестах он не отрабатывал. А тут еще круче.