ci: tag and release main from Conventional Commits

.github/workflows/release.yml

@@ -0,0 +1,97 @@
+name: Release
+
+on:
+  workflow_run:
+    workflows: [CI]
+    types: [completed]
+
+permissions:
+  contents: write
+
+jobs:
+  tag-and-release:
+    # Chains off the same trusted CI-on-main signal as CD, so a release only
+    # ever follows a green build of a commit that actually landed on main.
+    if: >-
+      github.event.workflow_run.conclusion == 'success' &&
+      github.event.workflow_run.head_branch == 'main' &&
+      github.event.workflow_run.event == 'push'
+    runs-on: ubuntu-latest
+    env:
+      RELEASE_SHA: ${{ github.event.workflow_run.head_sha }}
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          ref: ${{ env.RELEASE_SHA }}
+          fetch-depth: 0
+
+      - name: Determine the next version from conventional commits
+        id: version
+        run: |
+          set -euo pipefail
+          last_tag="$(git tag --list 'v*.*.*' --sort=-v:refname | head -n1)"
+          if [[ -n "$last_tag" ]]; then
+            range="${last_tag}..${RELEASE_SHA}"
+            base="${last_tag#v}"
+          else
+            range="${RELEASE_SHA}"
+            base="0.0.0"
+          fi
+
+          if [[ -z "$(git log "$range" --oneline 2>/dev/null)" ]]; then
+            echo "No commits since ${last_tag:-the start of history}; nothing to release."
+            echo "bump=none" >> "$GITHUB_OUTPUT"
+            exit 0
+          fi
+
+          subjects="$(git log "$range" --pretty=%s)"
+          bodies="$(git log "$range" --pretty=%b)"
+
+          # Conventional Commits: a feature earns a minor release, a fix a
+          # patch, and a declared breaking change (either `type!:` or a
+          # BREAKING CHANGE footer) always wins regardless of what else is in
+          # the range. Anything else (docs/ci/build/test/chore) is
+          # deliberately not release-worthy on its own.
+          bump=none
+          if grep -qE '^[a-z]+(\([^)]*\))?!:' <<<"$subjects" || grep -q 'BREAKING CHANGE' <<<"$bodies"; then
+            bump=major
+          elif grep -qE '^feat(\([^)]*\))?:' <<<"$subjects"; then
+            bump=minor
+          elif grep -qE '^fix(\([^)]*\))?:' <<<"$subjects"; then
+            bump=patch
+          fi
+
+          if [[ "$bump" == none ]]; then
+            echo "No feat/fix/breaking change since ${last_tag:-the start of history}; skipping the release."
+            echo "bump=none" >> "$GITHUB_OUTPUT"
+            exit 0
+          fi
+
+          IFS=. read -r major minor patch <<<"$base"
+          case "$bump" in
+            major) major=$((major + 1)); minor=0; patch=0 ;;
+            minor) minor=$((minor + 1)); patch=0 ;;
+            patch) patch=$((patch + 1)) ;;
+          esac
+
+          echo "bump=$bump" >> "$GITHUB_OUTPUT"
+          echo "version=v${major}.${minor}.${patch}" >> "$GITHUB_OUTPUT"
+
+      - name: Tag and publish the release
+        if: steps.version.outputs.bump != 'none'
+        env:
+          VERSION: ${{ steps.version.outputs.version }}
+        run: |
+          set -euo pipefail
+          if git rev-parse "$VERSION" >/dev/null 2>&1; then
+            echo "$VERSION already exists; skipping."
+            exit 0
+          fi
+          git tag -a "$VERSION" "$RELEASE_SHA" -m "$VERSION"
+          git push origin "$VERSION"
+          gh release create "$VERSION" \
+            --repo "${{ github.repository }}" \
+            --title "$VERSION" \
+            --target "$RELEASE_SHA" \
+            --generate-notes

README.md

@@ -61,6 +61,18 @@ Successful PR CI runs are merged automatically only for trusted same-repository
 and Dependabot. Forks, drafts, and untrusted author associations are deliberately skipped;
 repository branch-protection and review requirements continue to apply.
 
+### Releases
+
+Every push to `main` that passes CI is scanned for
+[Conventional Commits](https://www.conventionalcommits.org/) since the last tag. A `feat:`
+commit earns a minor release, `fix:` a patch release, and a declared breaking change
+(`type!:` or a `BREAKING CHANGE` footer) always wins with a major release. A range with none
+of those — only `docs:`, `ci:`, `build:`, `test:`, or `chore:` commits, as with most
+Dependabot bumps — is deliberately left unreleased. When a release is warranted, the
+workflow tags `main` (`vMAJOR.MINOR.PATCH`) and publishes a GitHub Release with
+auto-generated notes. Tags are never created by hand, and nothing is ever tagged off a
+branch other than `main`.
+
 ## Serving backends
 
 `ROUTER_BACKEND=mock` (the default) keeps CI deterministic and GPU-free.