[PATCH qemu-server] debian: add maintscript to remove unused file

[Maximiliano Sandoval <m.sandoval@proxmox.com>]

The conffile was moved to LIDBIR in in 4093c3f4a but there was no
associated cleanup.

If one starts from a version of Proxmox VE older than 9, then the the
configuration would be at /etc. If the machine is then updated to
version 9, then both versions will be present, with the version at /etc
having a higher priority as per modules-load.d(5). In such a case, any
changes made in the packaged configuration will be ignored.

The rm_config (see dpkg-maintscript-helper(1)) is used to remove the
trailing config if it was not touched by the user. If the file was
touched by the user then it is automatically moved and we move it back
manually so that it continues to have higher preference.

Suggested-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
Signed-off-by: Maximiliano Sandoval <m.sandoval@proxmox.com>
---

Notes:
    Tested:
    
    1. Created pve 8 VM using the 8.4 iso
    2. Checked the version at /etc is present
    3. Updated to pve 9
    4. Checked that both versions are present
    5. Updated the qemu-server package using this patch
    6. Verified the file at /etc is not there
    
    During step 5. the following message can be seen:
    
        Removing obsolete conffile /etc/modules-load.d/qemu-server.conf ...
    
    If we edit the file before 5. then one would see
    
       Obsolete conffile /etc/modules-load.d/qemu-server.conf has been modified by you.
       Saving as /etc/modules-load.d/qemu-server.conf.dpkg-bak ...
       Moving qemu-server.conf.dpkg-bak back to qemu-server.conf
    
    and systemd-delta would still consider this as an override of the
    version at /usr/lib.
    
    Further reinstalls of the qemu-server package will leave alone this
    version of /etc/modules-load.d/qemu-server.conf.
    
    Note that the version at /etc will only have a higher preference over
    the one at /usr/lib if it is named exactly the same, thus we move it
    back rather than renaming it to, e.g. qemu-server-old.conf, as this
    would result in the union of both modules being loaded by
    systemd-modules-load.service at boot.

 debian/postinst                | 18 ++++++++++++++++++
 debian/qemu-server.maintscript |  1 +
 2 files changed, 19 insertions(+)
 create mode 100644 debian/postinst
 create mode 100644 debian/qemu-server.maintscript

diff --git a/debian/postinst b/debian/postinst
new file mode 100644
index 00000000..aff4a27e
--- /dev/null
+++ b/debian/postinst
@@ -0,0 +1,18 @@
+#!/bin/sh
+
+set -e
+
+#DEBHELPER#
+
+case "$1" in
+    configure)
+
+    if test -n "$2" && dpkg --compare-versions "$2" 'lt' '9.1.6'; then
+        if test -f  /etc/modules-load.d/qemu-server.conf.dpkg-bak; then
+            printf "Moving qemu-server.conf.dpkg-bak back to qemu-server.conf\n"
+            mv /etc/modules-load.d/qemu-server.conf.dpkg-bak /etc/modules-load.d/qemu-server.conf
+        fi
+    fi
+esac
+
+exit 0
diff --git a/debian/qemu-server.maintscript b/debian/qemu-server.maintscript
new file mode 100644
index 00000000..c48d470f
--- /dev/null
+++ b/debian/qemu-server.maintscript
@@ -0,0 +1 @@
+rm_conffile /etc/modules-load.d/qemu-server.conf 9.1.6~ qemu-server
-- 
2.47.3