Fix initramfs.conf move to ensure default values are upgraded

When we upgrade from a version earlier than 0.123, initramfs.conf is
transfered from initramfs-tools to initramfs-tools-core and is not
modified.  But if it has not been changed from the default shipped in
the old version, it should be upgraded to the new default.  An upgrade
directly from Debian stable (0.120+deb8u2) to testing (0.125) should
change BUSYBOX=yes to BUSYBOX=auto but does not.

Andreas Beckmann extracted and adapted the code from
dpkg-maintscript-helper for conffile removal and renaming, that has
the necessary checks.  I've simplified that a little bit to reduce
code churn.

Thanks: Andreas Beckmann <anbe@debian.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Closes: #822671, #825929

4 files changed, 117 insertions, 19 deletions

diff --git a/debian/initramfs-tools-core.postinst b/debian/initramfs-tools-core.postinst
index cd69e02..395e997 100644
--- a/debian/initramfs-tools-core.postinst
+++ b/debian/initramfs-tools-core.postinst
@@ -7,15 +7,37 @@ if [ ! -e /etc/initramfs-tools/modules ]; then
 		> /etc/initramfs-tools/modules
 fi
 
+mvverbose=-v
+
+# from dpkg-maintscript-helper, modified
+ensure_package_owns_file() {
+	local PACKAGE="$1"
+	local FILE="$2"
+
+	dpkg-query -L "$PACKAGE" | grep -F -q -x "$FILE"
+}
+
+# from dpkg-maintscript-helper, modified
+finish_mv_conffile() {
+	local CONFFILE="$1"
+	local PACKAGE="$2"
+
+	rm $mvverbose -f "$CONFFILE.dpkg-remove"
+
+	[ -e "$CONFFILE.dpkg-backup" ] || return 0
+	ensure_package_owns_file "$PACKAGE" "$CONFFILE" || return 0
+
+	echo "Preserving user changes to $CONFFILE (now owned by $PACKAGE)..."
+	if [ -e "$CONFFILE" ]; then
+		mv $mvverbose -f "$CONFFILE" "$CONFFILE.dpkg-new"
+	fi
+	mv $mvverbose -f "$CONFFILE.dpkg-backup" "$CONFFILE"
+}
+
 # When installing as a new dependency of initramfs-tools, or upgrading
 # from <0.123, we need to move initramfs.conf back into place.
-if [ "$1" = configure ] && dpkg --compare-versions "$2" lt 0.123~ && \
-   [ -f /etc/initramfs-tools/initramfs.conf.dpkg-backup ]; then
-	# On fresh installation ($2 is empty), overwrite the shipped
-	# initramfs.conf.  Otherwise use -n to avoid overwriting user
-	# configuration if somehow both files exist.
-	mv ${2:+-n} /etc/initramfs-tools/initramfs.conf.dpkg-backup \
-		/etc/initramfs-tools/initramfs.conf
+if [ "$1" = configure ] && dpkg --compare-versions "$2" lt 0.123~; then
+	finish_mv_conffile /etc/initramfs-tools/initramfs.conf initramfs-tools-core
 fi
 
 #DEBHELPER#
diff --git a/debian/initramfs-tools.postinst b/debian/initramfs-tools.postinst
index 72e8b97..4e35c79 100644
--- a/debian/initramfs-tools.postinst
+++ b/debian/initramfs-tools.postinst
@@ -2,12 +2,37 @@
 
 set -e
 
+mvverbose=-v
+
+# from dpkg-maintscript-helper, modified
+ensure_package_owns_file() {
+	local PACKAGE="$1"
+	local FILE="$2"
+
+	dpkg-query -L "$PACKAGE" | grep -F -q -x "$FILE"
+}
+
+# from dpkg-maintscript-helper, modified
+finish_mv_conffile() {
+	local CONFFILE="$1"
+	local PACKAGE="$2"
+
+	rm $mvverbose -f "$CONFFILE.dpkg-remove"
+
+	[ -e "$CONFFILE.dpkg-backup" ] || return 0
+	ensure_package_owns_file "$PACKAGE" "$CONFFILE" || return 0
+
+	echo "Preserving user changes to $CONFFILE (now owned by $PACKAGE)..."
+	if [ -e "$CONFFILE" ]; then
+		mv $mvverbose -f "$CONFFILE" "$CONFFILE.dpkg-new"
+	fi
+	mv $mvverbose -f "$CONFFILE.dpkg-backup" "$CONFFILE"
+}
+
 # If initramfs-tools-core was fully upgraded to 0.123 before our
 # preinst ran, we need to move initramfs.conf back into place.
-if [ "$1" = configure ] && [ -n "$2" ] && dpkg --compare-versions "$2" lt 0.123~ && \
-   [ -f /etc/initramfs-tools/initramfs.conf.dpkg-backup ]; then
-	mv -n /etc/initramfs-tools/initramfs.conf.dpkg-backup \
-		/etc/initramfs-tools/initramfs.conf
+if [ "$1" = configure ] && [ -n "$2" ] && dpkg --compare-versions "$2" lt 0.123~; then
+	finish_mv_conffile /etc/initramfs-tools/initramfs.conf initramfs-tools-core
 fi
 
 # Regenerate initramfs whenever we go to dpkg state `installed'
diff --git a/debian/initramfs-tools.postrm b/debian/initramfs-tools.postrm
index 58e36e2..69f1dca 100755
--- a/debian/initramfs-tools.postrm
+++ b/debian/initramfs-tools.postrm
@@ -2,12 +2,37 @@
 
 set -e
 
+mvverbose=-v
+
+# from dpkg-maintscript-helper, modified
+ensure_package_owns_file() {
+	local PACKAGE="$1"
+	local FILE="$2"
+
+	dpkg-query -L "$PACKAGE" | grep -F -q -x "$FILE"
+}
+
+# from dpkg-maintscript-helper
+abort_rm_conffile() {
+	local CONFFILE="$1"
+	local PACKAGE="$2"
+
+	ensure_package_owns_file "$PACKAGE" "$CONFFILE" || return 0
+
+	if [ -e "$CONFFILE.dpkg-remove" ]; then
+		echo "Reinstalling $CONFFILE that was moved away"
+		mv $mvverbose "$CONFFILE.dpkg-remove" "$CONFFILE"
+	fi
+	if [ -e "$CONFFILE.dpkg-backup" ]; then
+		echo "Reinstalling $CONFFILE that was backupped"
+		mv $mvverbose "$CONFFILE.dpkg-backup" "$CONFFILE"
+	fi
+}
+
 # If aborting an upgrade from <0.123, we need to move initramfs.conf back
 # into place.
-if [ "$1" = abort-upgrade ] && dpkg --compare-versions "$2" lt 0.123~ && \
-   [ -f /etc/initramfs-tools/initramfs.conf.dpkg-backup ]; then
-	mv -n /etc/initramfs-tools/initramfs.conf.dpkg-backup \
-		/etc/initramfs-tools/initramfs.conf
+if [ "$1" = abort-upgrade ] && dpkg --compare-versions "$2" lt 0.123~; then
+	abort_rm_conffile /etc/initramfs-tools/initramfs.conf initramfs-tools
 fi
 
 #DEBHELPER#
diff --git a/debian/initramfs-tools.preinst b/debian/initramfs-tools.preinst
index c9b5168..99144bb 100755
--- a/debian/initramfs-tools.preinst
+++ b/debian/initramfs-tools.preinst
@@ -2,14 +2,40 @@
 
 set -e
 
+mvverbose=-v
+
+# from dpkg-maintscript-helper, modified
+ensure_package_owns_file() {
+	local PACKAGE="$1"
+	local FILE="$2"
+
+	dpkg-query -L "$PACKAGE" | grep -F -q -x "$FILE"
+}
+
+# from dpkg-maintscript-helper
+prepare_rm_conffile() {
+	local CONFFILE="$1"
+	local PACKAGE="$2"
+
+	[ -e "$CONFFILE" ] || return 0
+	ensure_package_owns_file "$PACKAGE" "$CONFFILE" || return 0
+
+	local md5sum="$(md5sum $CONFFILE | sed -e 's/ .*//')"
+	local old_md5sum="$(dpkg-query -W -f='${Conffiles}' $PACKAGE | \
+		sed -n -e "\' $CONFFILE ' { s/ obsolete$//; s/.* //; p }")"
+	if [ "$md5sum" != "$old_md5sum" ]; then
+		mv $mvverbose -f "$CONFFILE" "$CONFFILE.dpkg-backup"
+	else
+		mv $mvverbose -f "$CONFFILE" "$CONFFILE.dpkg-remove"
+	fi
+}
+
 # When upgrading from <0.123, we need to move initramfs.conf away so
 # dpkg will stop remembering it as an 'obsolete' conffile for us.  The
 # postinst of either initramfs-tools or initramfs-tools-core will move
 # it back.
-if [ "$1" = upgrade ] && dpkg --compare-versions "$2" lt 0.123~ && \
-   [ -f /etc/initramfs-tools/initramfs.conf ]; then
-	mv /etc/initramfs-tools/initramfs.conf \
-		/etc/initramfs-tools/initramfs.conf.dpkg-backup
+if [ "$1" = upgrade ] && dpkg --compare-versions "$2" lt 0.123~; then
+	prepare_rm_conffile /etc/initramfs-tools/initramfs.conf initramfs-tools
 fi
 
 #DEBHELPER#