refactor(release): move file helpers into files package

https://chatgpt.com/share/69454ef4-e038-800f-a14b-4e633e76f241

src/pkgmgr/actions/release/files/debian.py

@@ -0,0 +1,74 @@
+from __future__ import annotations
+
+import os
+from datetime import datetime
+from typing import Optional, Tuple
+
+from pkgmgr.core.git.queries import get_config_value
+
+
+def _get_debian_author() -> Tuple[str, str]:
+    name = os.environ.get("DEBFULLNAME")
+    email = os.environ.get("DEBEMAIL")
+
+    if not name:
+        name = os.environ.get("GIT_AUTHOR_NAME")
+    if not email:
+        email = os.environ.get("GIT_AUTHOR_EMAIL")
+
+    if not name:
+        name = get_config_value("user.name")
+    if not email:
+        email = get_config_value("user.email")
+
+    if not name:
+        name = "Unknown Maintainer"
+    if not email:
+        email = "unknown@example.com"
+
+    return name, email
+
+
+def update_debian_changelog(
+    debian_changelog_path: str,
+    package_name: str,
+    new_version: str,
+    message: Optional[str] = None,
+    preview: bool = False,
+) -> None:
+    if not os.path.exists(debian_changelog_path):
+        print("[INFO] debian/changelog not found, skipping.")
+        return
+
+    debian_version = f"{new_version}-1"
+    now = datetime.now().astimezone()
+    date_str = now.strftime("%a, %d %b %Y %H:%M:%S %z")
+
+    author_name, author_email = _get_debian_author()
+
+    first_line = f"{package_name} ({debian_version}) unstable; urgency=medium"
+    body_line = message.strip() if message else f"Automated release {new_version}."
+    stanza = (
+        f"{first_line}\n\n"
+        f"  * {body_line}\n\n"
+        f" -- {author_name} <{author_email}>  {date_str}\n\n"
+    )
+
+    if preview:
+        print(
+            "[PREVIEW] Would prepend the following stanza to debian/changelog:\n"
+            f"{stanza}"
+        )
+        return
+
+    try:
+        with open(debian_changelog_path, "r", encoding="utf-8") as f:
+            existing = f.read()
+    except Exception as exc:
+        print(f"[WARN] Could not read debian/changelog: {exc}")
+        existing = ""
+
+    with open(debian_changelog_path, "w", encoding="utf-8") as f:
+        f.write(stanza + existing)
+
+    print(f"Updated debian/changelog with version {debian_version}")