ci: added git-cliff changelog automation

CONTRIBUTING.md

@@ -74,6 +74,63 @@ writeLines(pak::pkg_system_requirements("devtools", "ubuntu", "22.04"))
 To remove the local virtual Python environment, delete the `r-acro` folder.
 On GNU/Linux this is typically located in `~/.virtualenvs`
 
+## Pull Request Titles
+
+Use [Conventional Commits](https://www.conventionalcommits.org) for PR titles (squash-merge messages). This allows automated changelog generation. Common prefixes:
+
+```
+feat — new feature
+fix — bug fix
+docs — documentation changes
+style — formatting/styling (no code logic)
+refactor — code changes without feature/bug impact
+perf — performance improvements
+test — adding/updating tests
+build — changes to build system or dependencies
+ci — changes to CI config/scripts
+chore — miscellaneous maintenance tasks
+revert — reverts an earlier commit
+```
+
+## Release Workflow
+
+`NEWS.md` is generated locally before each release using [git-cliff](https://github.com/orhun/git-cliff). It reads merged PR titles (via squash-merge commit messages) since the last release tag and formats them to match the existing changelog style.
+
+### Install git-cliff
+
+```shell
+# pip
+pip install git-cliff
+
+# uv
+uv tool install git-cliff
+
+# homebrew (macOS / Linux)
+brew install git-cliff
+```
+
+### Generate the changelog entry
+
+Run the following on `main` immediately before tagging a new release, replacing `X.Y.Z` with the new version:
+
+```shell
+git cliff --config cliff.toml --unreleased --tag "VX.Y.Z" --prepend NEWS.md
+```
+
+Review and edit `NEWS.md` as needed (e.g. to add extra context or merge duplicate entries), then commit:
+
+```shell
+git add NEWS.md
+git commit -m "docs: update changelog"
+git tag VX.Y.Z
+```
+
+The configuration lives in `cliff.toml` at the repository root. It automatically:
+
+- Converts `(#NNN)` PR references into markdown links.
+- Skips noise commits (pre-commit auto-fixes, changelog and release-prep commits).
+- Filters out commits that do not follow Conventional Commits (see [Pull Request Titles](#pull-request-titles)).
+
 ## CRAN Submission
 
 A useful command to run before submitting:

cliff.toml

@@ -0,0 +1,42 @@
+[changelog]
+header = ""
+body = """
+{% if version %}\
+# acro {{ version | trim_start_matches(pat="v") }}
+
+{% else %}\
+# Unreleased
+
+{% endif %}\
+{% for commit in commits -%}
+*   {% if commit.scope %}{{ commit.group }}({{ commit.scope }}): {% else %}{{ commit.group }}: {% endif %}{{ commit.message | trim }}
+{% endfor %}\
+"""
+trim = true
+footer = ""
+
+[git]
+conventional_commits = true
+filter_unconventional = true
+tag_pattern = "V[0-9]+\\.[0-9]+\\.[0-9]+"
+
+commit_preprocessors = [
+    { pattern = ' \(#(\d+)\)', replace = ' ([#$1](https://github.com/AI-SDC/ACRO-R/pull/$1))' },
+]
+
+commit_parsers = [
+    { message = "^\\[pre-commit", skip = true },
+    { message = "^docs: update changelog", skip = true },
+    { message = "^chore: prepare", skip = true },
+    { message = "^feat", group = "feat" },
+    { message = "^fix", group = "fix" },
+    { message = "^docs", group = "docs" },
+    { message = "^chore", group = "chore" },
+    { message = "^ci", group = "ci" },
+    { message = "^refactor", group = "refactor" },
+    { message = "^test", group = "test" },
+    { message = "^build", group = "build" },
+    { message = "^perf", group = "perf" },
+    { message = "^style", group = "style" },
+    { message = "^revert", group = "revert" },
+]