feat: add --version option

Add a top-level `--version` flag via an eager Typer root callback that reads
the installed package metadata (importlib.metadata) and prints
`datadog-slo-overrides <version>`, falling back to "unknown" if the
distribution metadata isn't available. Covered by a CLI test.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Yhoorneman

README.md

@@ -17,7 +17,7 @@
 [![Changelog](https://img.shields.io/badge/changelog-Keep%20a%20Changelog%201.1.0-orange)](https://keepachangelog.com/en/1.1.0/)
 [![Documentation: Diátaxis](https://img.shields.io/badge/docs-Di%C3%A1taxis-009485?logo=readthedocs&logoColor=white)](https://diataxis.fr/)
 [![Build](https://img.shields.io/badge/build-unknown-lightgrey)](https://github.com/features/actions)
-[![Coverage](https://img.shields.io/badge/coverage-61%25-orange)](https://coverage.readthedocs.io/)
+[![Coverage](https://img.shields.io/badge/coverage-62%25-orange)](https://coverage.readthedocs.io/)
 [![pyscn quality](https://img.shields.io/badge/pyscn-not%20rated-lightgrey)](https://pyscn.ludo-tech.org)
 
 CLI to set overrides idempotently for multiple SLO's

src/datadog_slo_overrides_cli/datadog_slo_overrides_cli.py

@@ -26,6 +26,8 @@
 import tomllib
 from dataclasses import dataclass
 from datetime import datetime
+from importlib.metadata import PackageNotFoundError
+from importlib.metadata import version as package_version
 from pathlib import Path
 from zoneinfo import ZoneInfo, ZoneInfoNotFoundError
 
@@ -69,6 +71,7 @@
 APP_KEY_ENV = 'DD_APP_KEY'
 
 APP_NAME = 'datadog-slo-overrides'
+PACKAGE_NAME = 'datadog_slo_overrides_cli'
 
 
 def config_dir() -> Path:
@@ -739,6 +742,34 @@ def execute(cfg: RunConfig) -> int:
 )
 
 
+def _version_callback(value: bool) -> None:
+    """Print the package version and exit when ``--version`` is passed."""
+    if not value:
+        return
+    try:
+        installed = package_version(PACKAGE_NAME)
+    except PackageNotFoundError:
+        installed = 'unknown'
+    typer.echo(f'{APP_NAME} {installed}')
+    raise typer.Exit
+
+
+@app.callback()
+def _root(
+    _version: bool = typer.Option(
+        False,
+        '--version',
+        callback=_version_callback,
+        is_eager=True,
+        help='Show the version and exit.',
+    ),
+) -> None:
+    """Set Datadog SLO corrections on multiple SLOs, selected by tag.
+
+    Dry-run by default; --apply to write. See README.md.
+    """
+
+
 @app.command(no_args_is_help=True)
 def run(
     tag: list[str] = typer.Option(

tests/test_datadog_slo_overrides_cli.py

@@ -190,6 +190,13 @@ def test_init_config_writes_template_and_guards_overwrite(tmp_path: Path) -> Non
     assert second.exit_code != 0
 
 
+def test_version_option() -> None:
+    """--version prints the app name and version, then exits 0."""
+    result = runner.invoke(app, ['--version'])
+    assert result.exit_code == 0
+    assert 'datadog-slo-overrides' in result.output
+
+
 def test_load_direnv_env_success(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
     """A successful ``direnv export json`` is parsed into the exported variables."""
     (tmp_path / '.envrc').write_text('export DD_API_KEY=k\n')