feat: track Decman configuration

system-config/scripts/refresh_orphan_guards.py

@@ -0,0 +1,58 @@
+#!/usr/bin/env python3
+"""Refresh dependency packages that Decman must ignore to guarantee no removal."""
+
+from __future__ import annotations
+
+import subprocess
+from pathlib import Path
+
+import pyalpm
+
+ROOT = Path(__file__).resolve().parents[1]
+OUTPUT = ROOT / "packages" / "ignored"
+
+
+def repository_names(handle: pyalpm.Handle) -> set[str]:
+    return {
+        package.name
+        for database in handle.get_syncdbs()
+        for package in database.pkgcache
+    }
+
+
+def deep_orphans(handle: pyalpm.Handle, predicate) -> set[str]:
+    local = {package.name: package for package in handle.get_localdb().pkgcache}
+    candidates = {
+        package.name
+        for package in local.values()
+        if package.reason == pyalpm.PKG_REASON_DEPEND and predicate(package.name)
+    }
+    while True:
+        retained = {
+            name
+            for name in candidates
+            if not (set(local[name].compute_requiredby()) - candidates)
+        }
+        if retained == candidates:
+            return retained
+        candidates = retained
+
+
+def write(name: str, values: set[str]) -> None:
+    (OUTPUT / name).write_text("\n".join(sorted(values)) + "\n", encoding="utf-8")
+
+
+def main() -> None:
+    handle = pyalpm.Handle("/", "/var/lib/pacman")
+    repositories = subprocess.run(
+        ["pacman-conf", "--repo-list"], check=True, text=True, stdout=subprocess.PIPE
+    ).stdout.split()
+    for repository in repositories:
+        handle.register_syncdb(repository, 0)
+    native = repository_names(handle)
+    write("repo-dependencies.txt", deep_orphans(handle, lambda name: name in native))
+    write("aur-dependencies.txt", deep_orphans(handle, lambda name: name not in native))
+
+
+if __name__ == "__main__":
+    main()