Probe the RPM filename nfpm actually publishes (#175)

nfpm re-renders semver versions into the RPM filename, so `2025.08.03` ships as `2025.8.3`. The existence probe asked artifactapi for the raw metadata version, always got a 404, and rebuilt and republished `nzbget_exporter` and `unkin-ca-certificates` on every pipeline run.

- add `nfpm_rpm_version`/`rpm_file_name` mirroring nfpm rendering
- build the probe filename through `rpm_file_name`
- drop dead `normalize_version` and `get_package_full_name`
- cover the nfpm rendering table and the probed URL in tests

Reviewed-on: #175
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>

tests/test_build.py

@@ -0,0 +1,76 @@
+"""Tests for the RPM filename tools/build reconstructs when probing artifactapi.
+
+The expected values below were captured from the real nfpm; they are the names
+the publish step actually uploads, so the existence probe has to ask for
+exactly these or it 404s and rebuilds forever.
+"""
+
+import importlib.machinery
+import importlib.util
+from pathlib import Path
+
+import pytest
+
+REPO_ROOT = Path(__file__).parent.parent
+
+_loader = importlib.machinery.SourceFileLoader(
+    "rpmbuilder_build", str(REPO_ROOT / "tools" / "build")
+)
+_spec = importlib.util.spec_from_loader(_loader.name, _loader)
+build = importlib.util.module_from_spec(_spec)
+_loader.exec_module(build)
+
+
+# nfpm output for `version: <input>` with release 1, arch amd64
+NFPM_VERSIONS = [
+    ("2025.08.03", "2025.8.3"),
+    ("2025.07.13", "2025.7.13"),
+    ("1.05.0", "1.5.0"),
+    ("10.02.01", "10.2.1"),
+    ("0.0.09", "0.0.9"),
+    ("0.6.1", "0.6.1"),
+    ("1.2.3", "1.2.3"),
+    ("1.05", "1.5.0"),
+    ("08", "8.0.0"),
+    ("1.0.0-rc1", "1.0.0~rc1"),
+    ("1.05.0-rc1", "1.5.0~rc1"),
+    ("1.0.0-rc.1", "1.0.0~rc.1"),
+    # not semver: nfpm leaves these verbatim, so we must too
+    ("1.02.3.4", "1.02.3.4"),
+    ("2025.08.03.01", "2025.08.03.01"),
+    ("1.2.3.4", "1.2.3.4"),
+    ("1.0.0-rc.01", "1.0.0-rc.01"),
+]
+
+
+@pytest.mark.parametrize("version,expected", NFPM_VERSIONS)
+def test_nfpm_rpm_version(version, expected):
+    assert build.nfpm_rpm_version(version) == expected
+
+
+def test_rpm_file_name_matches_nfpm_output():
+    assert (
+        build.rpm_file_name("nzbget_exporter", "2025.08.03", "1.el9", "amd64")
+        == "nzbget_exporter-2025.8.3-1.el9.x86_64.rpm"
+    )
+
+
+def test_check_package_exists_probes_published_filename(monkeypatch):
+    """A zero-padded version must not probe a filename nfpm can never produce."""
+    probed = []
+
+    class _Session:
+        def get(self, url, timeout=None):
+            probed.append(url)
+            return type("R", (), {"status_code": 404})()
+
+    monkeypatch.setattr(build, "_artifactapi_session", _Session())
+
+    assert not build.check_package_exists(
+        "nzbget_exporter", "2025.08.03", "1.el9", "almalinux/el9", "amd64"
+    )
+    expected = (
+        "https://artifactapi.k8s.syd1.au.unkin.net/api/v2/remotes/rpm-vendor-el9"
+        "/files/Packages/nzbget_exporter-2025.8.3-1.el9.x86_64.rpm"
+    )
+    assert probed == [expected]