chore(ci): automate release process

This PR significant changes the release process, by mostly automating it
all. The docs on creating releases has been updated and moved into the
`docs/` folder (anticipating that we will use MkDocs eventually).

The check step in the build pipeline has been removed, as it is
redundant given that cibuildwheel already does checks.

Signed-off-by: JP-Ellis <[email protected]>

.github/CHANGELOG.md.j2

@@ -0,0 +1,19 @@
+{% for entry in tree %}
+
+## {{ entry.version }}{% if entry.date %} ({{ entry.date }}){% endif %}
+
+{% for change_key, changes in entry.changes.items() %}
+
+{% if change_key %}
+### {{ change_key }}
+{% endif %}
+
+{% for change in changes %}
+{% if change.scope %}
+-   **{{ change.scope }}**: {{ change.message }}
+{% elif change.message %}
+-   {{ change.message }}
+{% endif %}
+{% endfor %}
+{% endfor %}
+{% endfor %}

.github/workflows/build.yml

@@ -20,7 +20,7 @@ env:
   CIBW_BUILD_FRONTEND: build
 
 jobs:
-  build-sdit:
+  build-sdist:
     name: Build source distribution
 
     if: github.event_name == 'push' || ! github.event.pull_request.draft
@@ -114,7 +114,7 @@ jobs:
   build-arm64:
     name: Build wheels on ${{ matrix.os }} (arm64)
 
-    # As this requires emulation, it's not worth running on PRs
+    # As this requires emulation, it's not worth running on PRs or master
     if: >-
       github.event_name == 'push' &&
       startsWith(github.event.ref, 'refs/tags')
@@ -189,26 +189,75 @@ jobs:
           pipx run twine check --strict wheelhouse/*
 
   publish:
-    name: Publish wheels
+    name: Publish wheels and sdist
 
     if: github.event_name == 'push' && startsWith(github.event.ref, 'refs/tags/v')
     runs-on: ubuntu-latest
     environment: pypi
 
-    needs: [check]
+    needs:
+      - build-sdist
+      - build-x86_64
+      - build-arm64
 
     permissions:
       # Required for trusted publishing
       id-token: write
+      # Required for release creation
+      contents: write
 
     steps:
       - uses: actions/download-artifact@c850b930e6ba138125429b7e5c93fc707a7f8427 # v4
         with:
           path: wheels
+          merge-multiple: true
+
+      - name: Setup Python
+        uses: actions/setup-python@0a5c61591373683505ea898e09a3ea4f39ef2b9c # v5
+        with:
+          python-version: ${{ env.STABLE_PYTHON_VERSION }}
+
+      - name: Update changelog
+        id: changelog
+        run: |
+          pip install --upgrade commitizen
+
+          cz changelog \
+            --incremental \
+            --template .github/CHANGELOG.md.j2 \
+            --dry-run \
+            | tail -n+2 \
+            > ${{ runner.temp }}/changelog
+          echo -e "\n\n## Pull Requests\n\n" >> ${{ runner.temp }}/changelog
+
+          cz changelog \
+            --incremental \
+            --template .github/CHANGELOG.md.j2
+
+      - name: Generate release
+        id: release
+        uses: softprops/action-gh-release@v1
+        with:
+          files: wheels/*
+          body_path: ${{ runner.temp }}/changelog
+          draft: false
+          prerelease: false
+          generate_release_notes: true
 
       - name: Push build artifacts to PyPI
         uses: pypa/gh-action-pypi-publish@e53eb8b103ffcb59469888563dc324e3c8ba6f06 # v1.8.12
         with:
           skip-existing: true
           password: ${{ secrets.PYPI_TOKEN }}
           packages-dir: wheels
+
+      - name: Create PR for changelog update
+        uses: peter-evans/create-pull-request@v6
+        with:
+          token: ${{ secrets.GH_TOKEN }}
+          commit-message: "chore: update changelog ${{ github.ref_name }}"
+          title: "chore: update changelog"
+          body: |
+            This PR updates the changelog for ${{ github.ref_name }}.
+          branch: chore/update-changelog
+          base: master

docs/releases.md

@@ -0,0 +1,49 @@
+# Releases
+
+Pact Python is made available through both GitHub releases and PyPI. The GitHub releases also come with a summary of changes and contributions since the last release.
+
+The entire process is automated through the [build](https://github.com/pact-foundation/pact-python/actions?query=workflow%3Abuild) GitHub Action. A description of the process is provided [below](#build-pipeline).
+
+## Versioning
+
+Pact Python follows [semantic versioning](https://semver.org/). Breaking changes are indicated by a major version bump, new features by a minor version bump, and bug fixes by a patch version bump.
+
+There are a couple of exceptions to the [semantic versioning](https://semver.org/) rules:
+
+-   Dropping support for a Python version is not considered a breaking change and is not necessarily accompanied by a major version bump.
+-   Private APIs are not considered part of the public API and are not subject to the same rules as the public API. They can be changed at any time without a major version bump. Private APIs are denoted by a leading underscore in the name. Please be aware that the distinction between public and private APIs will be made concrete from version 3 onwards, and best judgement is used in the meantime to determine what is public and what is private.
+-   Deprecations are not considered breaking changes and are not necessarily accompanied by a major version bump. Their removal is considered a breaking change and is accompanied by a major version bump.
+
+Any deviation from the the standard semantic versioning rules will be clearly documented in the release notes.
+
+The version is stored in `pact/__version__.py`. This file is automatically generated by [`hatch-vcs`](https://pypi.org/project/hatch-vcs/) and generates a version based on the latest version tag and the number of commits since that tag. Specifically:
+
+-   If the latest tag is `v1.2.3` and there have been no commits since then and the repository is clean, the version will be `1.2.3`.
+-   Otherwise, the version will take the form of `1.2.3.dev{N}+g{hash}` (or `1.2.3.dev{N}+g{hash}.d{date}` if there's a dirty repository) where `N` is the number of commits since the latest tag, `hash` is the short hash of the latest commit.
+
+## Build Pipeline
+
+The build pipeline is defined in `.github/workflows/build.yml`. It is triggered on PRs targeting `master`, pushes to the `master` branch, and on every new tag. The pipeline is responsible for building the package (both as source distribution, and compiled wheels), creating the GitHub release, and uploading artifacts to PyPI.
+
+### Build Steps
+
+The build steps generates the source distribution and wheels. This is done using [cibuildwheel](https://cibuildwheel.readthedocs.io/) to ensure that the wheels are compatible with a wide range of Python versions and platforms.
+
+In order to reduce the build time, the pipeline builds different sets of wheels depending on the trigger:
+
+| Trigger      | Platforms         | Wheels    |
+| ------------ | ----------------- | --------- |
+| Tag          | `x86_64`, `arm64` | all       |
+| `master`     | `x86_64`          | all       |
+| Pull Request | `x86_64`          | `cp312-*` |
+
+### Publish Step
+
+The publish step uses the `pypi` GitHub environment, and is gated behind a manual approval. The publish step is responsible for the following:
+
+-   Generating a changelog based on the conventional commits since the latest release.
+-   Generating a new GitHub release with the changelog.
+-   Uploading the source distribution and wheels to PyPI.
+-   Creating a PR to update the `CHANGELOD.md` file with the new release notes.
+
+While the generated changelog should be accurate, it may require some manual adjustments on the release page and in the PR.