Removes basic hook and rule check files.

Fixes Pr checks bug.
Adds documentations.

ci/check_pr_policies.py

@@ -34,7 +34,10 @@ def git_ref_exists(ref: str) -> bool:
     except subprocess.CalledProcessError:
         return False
 
-def resolve_target_ref() -> str:
+def is_pull_request_build() -> bool:
+    return bool(os.environ.get("CHANGE_ID"))
+
+def resolve_target_ref() -> str | None:
     raw = os.environ.get("CHANGE_TARGET", "").strip()
 
     candidates = []
@@ -52,13 +55,27 @@ def resolve_target_ref() -> str:
             if git_ref_exists(ref):
                 return ref
 
-    print("ERROR: Kein gültiger Ziel-Branch-Ref gefunden. Geprüft:", ", ".join(candidates))
-    sys.exit(1)
+    return None
 
 def changed_files():
     target = resolve_target_ref()
-    print(f"Vergleiche gegen Ziel-Ref: {target}")
-    out = run(f"git diff --name-only {target}...HEAD")
+
+    if target:
+        print(f"Vergleiche gegen Ziel-Ref: {target}")
+        out = run(f"git diff --name-only {target}...HEAD")
+        return [line.strip() for line in out.splitlines() if line.strip()]
+
+    if is_pull_request_build():
+        print("ERROR: Kein gültiger Ziel-Branch-Ref für PR-Build gefunden.")
+        sys.exit(1)
+
+    if git_ref_exists("HEAD~1"):
+        print("Kein Ziel-Branch-Ref gefunden, verwende HEAD~1 für Branch-Build.")
+        out = run("git diff --name-only HEAD~1..HEAD")
+        return [line.strip() for line in out.splitlines() if line.strip()]
+
+    print("Keine Vergleichsbasis gefunden, behandle alle versionierten Dateien als geändert.")
+    out = run("git ls-files")
     return [line.strip() for line in out.splitlines() if line.strip()]
 
 def is_cpp_file(path: Path) -> bool: