updater: add flags to apt conf to auto-resolve conffiles conflicts

fixes QubesOS/qubes-issues/issues/9072

(cherry picked from commit 009d2e4)

vmupdate/agent/entrypoint.py

@@ -56,6 +56,12 @@ def get_package_manager(os_data, log, log_handler, log_level, no_progress):
     If appropriate python package is not installed or `no_progress` is `True`
     cli based version is returned.
     """
+    requirements = {}
+    # plugins MUST be applied before import anything from package managers.
+    # in case of apt configuration is loaded on `import apt`.
+    for plugin in plugins.entrypoints:
+        plugin(os_data, log, requirements=requirements)
+
     if os_data["os_family"] == "Debian":
         try:
             from source.apt.apt_api import APT as PackageManager
@@ -82,10 +88,6 @@ def get_package_manager(os_data, log, log_handler, log_level, no_progress):
         raise NotImplementedError(
             "Only Debian, RedHat and ArchLinux based OS is supported.")
 
-    requirements = {}
-    for plugin in plugins.entrypoints:
-        plugin(os_data, log, requirements=requirements)
-
     pkg_mng = PackageManager(log_handler, log_level)
     pkg_mng.requirements = requirements
     return pkg_mng

vmupdate/agent/source/plugins/apt_keep_old_conffiles.py

@@ -0,0 +1,37 @@
+# coding=utf-8
+#
+# The Qubes OS Project, http://www.qubes-os.org
+#
+# Copyright (C) 2024  Piotr Bartman <prbartman@invisiblethingslab.com>
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
+# USA.
+
+APT_CONF = "/etc/apt/apt.conf.d/01qubes-update"
+
+
+def apt_keep_old_conffiles(os_data, log, **kwargs):
+    """
+    Always chose default behavior for when conflicts in apt conffiles appears.
+    """
+    if os_data["os_family"] != "Debian":
+        return
+
+    option = '''Dpkg::Options {
+   "--force-confdef";
+   "--force-confold";
+}'''
+    with open(APT_CONF, "w") as file:
+        file.write(f'\n{option}\n')